FAQ’s: General Information

It sounds as though you have an early model rail-mounted engine. The adjustable mounts really won’t work in these installations, as they were designed for rails that are approximately 2″ lower than yours. I’m not all sure why your engine wouldn’t line up after you lowered it back down to the original rails. This would presumably be the same level the engine was sitting prior to removal. – Updated: May 24, 2004

This answer is pending…

Whenever a head moves any amount at all, it usually will continue its upward movement by even persistent prying. If you decided to remove the studs (which is a very good idea, and is what we do on every engine we dissemble), you’ll have to spring for one of our stud removing tools from our online catalog – listed in with our “Specialty Tools”. These tools grip the tops of the studs by clamping around the threads using a threaded collet which doesn’t damage the threads. – Updated: January 10, 2004

With an engine on my work bench, at eye level, with classical music playing in the background, I routinely check valves without removing either of these components; but other than with center cabin engines (like Catalina 30’s, Tartans, Ericson 35’s, etc.), I can’t really imagine having the room to access the valve chamber without (at least) removing the carburetor. – Updated: January 10, 2004

Two years is not all that long for an Atomic 4 to be idle. Nonetheless, here are a few steps to help get it off to a good start:

1) Check for good quality oil (30 weight, or 10-30) up to the full mark on the dipstick.

2) Put several squirts of Marvel Mystery Oil in each spark plug hole (aiming the spout of the can away from the manifold side of the engine) so that most of the oil will reach the cylinder bores. Then rotate the engine on the starter while holding your thumb over each spark plug hole. There should be enough compression produced at each cylinder to make it virtually impossible to hold your thumb over any of the spark plug holes.

3) Remove the main passage plug from the bottom of the carburetor and operate the fuel pump to move some fuel through the entire fuel system, and catch it in a jar below the carburetor. A couple pints should be enough to insure that the fuel is flowing perfectly clean. Then reinstall the plug and operate the fuel pump again until the carburetor is charged with fuel.

4) Remove the distributor cap and clean off the contact surfaces of the points.

5) Turn the engine over until the points are closed (It will be easier to rotate the engine if the spark plugs are removed). Then turn the ignition switch “ON”; while holding the secondary coil lead approximately 1/4″ from the head, flick the points open and closed. Each time the points are opened, there should be a good secondary spark observed between the coil lead and the head.

Assuming that these checks all went without incident, you have confirmed that you have adequate compression, fuel to (and through) the carburetor, a good secondary discharge available and ready for delivery to each cylinder, and your engine should be ready to start.

In the event that you are relatively new to the Atomic 4, Here are a few tips on starting technique:

1) “Pumping the throttle” is totally ineffective in starting the Atomic 4. Since there is no accelerator pump within the carburetor, pumping the throttle has absolutely no effect on anything in terms of supplying more or less fuel to the engine.

2) If your engine tries to start, but falters and stops as soon as you stop cranking on the starter, it is likely simply not getting enough fuel to work itself out of the idle range and into the lower range of the main discharge nozzle of the carburetor (which occurs around 1000 RPM). After an engine is warmed up, it will tend to start OK in idle, but cold engines seldom will start and run within the idle range. They need to start and warm up in the lower range of the main discharge nozzle before they can be brought back to idle.

3) The best setting for the throttle during starting is solidly off of the idle stop, so as to uncover both idle ports and get you into the “off idle” range of operation. It’s somewhat better to err on the high side in terms of throttle setting. If your engine ends up racing the instant that it starts, you can back off a little on the throttle setting during future starts.

As soon as the engine starts, check for oil pressure leveling out at 40 psi or above (engine still cold), and for a good flow of water out of the exhaust. In a normal cooling system, there should be enough water flowing through the engine so that it builds up a bit of head as the exhaust pressure builds up enough to blow the water out of the back of the boat. This creates a “batching” effect at idle, as water moves through the exhaust system. – Updated: January 10, 2004

As a general rule, unless you plan to take sufficient time to debug things, and give your engine the chance to “settle back in”, I don’t like to see folks performing major maintenance or replacing a lot of components just prior to a long trip. I believe it makes more sense to take spare parts. I would reconsider this advice in cases where access to a particular component is so bad that changing it would be very difficult while at a strange port. In those cases, replacement prior to departing may make more sense.

Having said all that, you might consider the following (light) maintenance if there is no documentation of it having been done recently:

COOLING SYSTEM:

1) Remove the water jacket side plate for inspection (including the distribution cap on the inside of the “T” fitting). Replace any parts that show signs of corrosion, and thoroughly reseal the plate.

2) Remove the brass elbow from the rear outlet of the manifold. Inspect for blockage within the elbow and in the water jacket of the manifold just under the fitting. If you discover a lot of crud just below this fitting, you can most likely remove it by scraping around with a small screwdriver or part of a coat hanger.

3) Remove the thermostat for cleaning (soaking in vinegar overnight).

4) Check all water hoses for general condition, and replace any that appear soft.

FUEL SYSTEM:

1) Insure that there is a good primary fuel filter installed between the tank and the fuel pump and a small inline filter between the fuel pump and carburetor. If you do not currently have a good primary filter, the RACOR filter from West Marine (for gasoline engines, and with a water separator) works very well.

2) If you have decent access to the main passage plug in the bottom of the carburetor, I recommend removing it and catching all the fuel in a small glass jar. All of the fuel in the carburetor will drain out through this plug, along with any dirt that may have been lurking there and getting ready to enter (or try to enter) and pass through the main jet.

With the main passage plug still removed, operate the fuel pump and flush at least a couple pints of fuel through the entire system and out through the main passage plug. When the fuel appears perfectly clean, reinstall the passage plug, being careful to not over-tighten and damage the fiber washer under the head of the plug, and work the fuel pump to recharge the carburetor

IGNITION (ELECTRICAL) SYSTEM:

1) Replace spark plugs, points and condenser, and check spark plug wires and the alternator belt for cracks and brittleness.

NOTE: The most common reason that ignition systems break down, in cases where an engine has been reasonably well maintained, is that the primary electrical circuit between the starter solenoid and the positive terminal of the coil develops a bad connection.

2) Inspect as much of the wiring between the engine and the cockpit as possible; but ultimately, my recommendation is to have a short jumper wire prepared to connect between the big battery cable on the starter solenoid and the positive terminal of the coil. This wire, when installed, will bypass all of the circuit (some of which you probably will not even be able to see) and provide positive ignition.

Remember that whenever this jumper wire is installed, it is equivalent to turning the ignition switch to the “ON” position, so be sure to remove it whenever you are not operating the engine.

RECOMMENDED SPARE PARTS:

1) Coil

2) Four new plugs

3) Spare fuel pump

4) Spare water pump

5) Three or four feet of engine water hose, fuel line (with appropriate size hose clamps), and a small roll of electrical wire (12 or 14 gauge).

6) A roll of good quality electrical tape.

7) Spare filter elements for any filters you have on board.

8) Spare alternator. This item is obviously optional due to the relatively high cost, and the space required to store it. I include it here simply because most of us rely so heavily on a good source of DC power for so many of the things that we have grown to consider essential.

RECOMMENDED TOOLS (In addition to normal hand tools and a copy of the Moyer Marine Service and Overhaul Manual):

1) A small digital volt/ohm meter.

2) A three-foot length of 14 gauge wire with a ring terminal on one end and a clip on the other. This wire can be used to “hot wire” the ignition system in the event of a failure of the primary circuit within the boat’s electrical system.

3) Electrical crimping tool and a small supply of ring terminals, butt splices, etc.

4) Remote starter switch (available for about $10 at most auto parts stores).

I hope this helps you to get started. Hopefully, as your knowledge of the engine grows, you’ll be able to add more items to this list which make sense to you, given your particular boating style and specific plans for your trip. – Updated: January 9, 2004

All Atomic-4 engines run in a counter-clockwise (LH) rotation as you would be in front of the engine, facing the flywheel. This means that as you would be facing the prop from behind a boat with a direct drive engine, the prop would be turning in a clockwise (RH) direction.

If your engine has a gear reduction unit installed (either a V-drive, or a standard 2 to 1 gear reduction unit), the prop would turn in the opposite direction (LH).

A V-drive unit is quite easy to identify, since the engine would be installed with the flywheel facing the rear of the boat.

A standard 2 to 1 gear reduction unit would be bolted to the rear of the engine, and the engine would be installed with the flywheel facing the front of the boat. The gear reduction unit has a “bell-shaped” housing that extends approximately 8 inches behind the reversing gear. Gear reduction models of the Atomic-4 can also be identified by the fact that they have four-bolt propeller shaft couplings, instead of the three-bolt couplings used on direct drive engines. – Updated: January 4, 2004

Your instinct that the (relatively) low compression in cylinder two somehow relates to the “0” compression in number one is very astute. Questions concerning the way in which certain findings relate to each other always take me back to my Air Force career in aircraft accident investigation.

We always held strongly to the concept of a single primary cause of accidents. This meant that as findings of various failures and discrepancies emerged during the investigation, we wouldn’t rest until we identified the cause and effect of all the findings and arranged them into a specific sequence of events that led to the accident. In this way, one could eventually (by looking further and further upstream in the sequence) discover the single original failure which made a particular accident inevitable.

Applying this rationale to your situation, I can see a possible sequence of events, starting with a partial head gasket failure between the first two cylinders.

We know from historical precedence that head gasket failures typically occur between two adjacent cylinders, that they lead to some lessening of compression, and that they frequently result in cooling water getting into the combustion chambers of the adjacent cylinders.

Whenever a small amount of water continues to enter a cylinder, the likelihood of valves sticking can also be expected to increase, until one of the valves (probably an exhaust valve in the first cylinder in your case) becomes stuck in the open position.

A bit of background information would probably have come to the accident board’s attention by this time, which is that engines throughout most of the 1970’s had asbestos head gaskets installed by the factory. These were extremely tough gaskets, and they seldom failed catastrophically. They would, however, become more and more brittle, until the constant sequencing of compression back and forth between any two adjacent cylinders eventually led to a miniscule amount of movement between the gasket and mating surfaces of the block and head.

This condition could exist for years as nothing more than a slight reduction in compression in the two adjacent cylinders. However, if this movement between the head gasket and block/head mating surfaces progresses to the point that it intercepts one or more of the nearby cooling water passages, then small amounts of water would be drawn into one or both of the affected cylinders.

With this “suspected” sequence of events giving direction to our investigation, we would, of course, look for supporting evidence. If your boat had crashed into a mountain side, we would have been looking for pieces of the first and second combustion chambers, so that we could inspect them for physical evidence of water damage (rust-colored residue mostly).

Thankfully, your boat hasn’t crashed. So, in terms of what to do, two things come to mind:

1) You could decide to make an attempt to free the stuck valve in the first cylinder by inserting a bent screwdriver or “L” shaped Allen head wrench in through the spark plug hole and pressing on top of the valve.

If you’re able to free the valve, you could squirt Marvel Mystery Oil into the first two spark plug holes and try to restore the condition of the first two cylinders to that which existed prior to the valve sticking. If compression readings continue to reflect 120 psi in the last two cylinders and 80-ish in the first two, you would have additional evidence that a head gasket might be the cause.

2) If you’re unable to free the valve, you’ll likely have to remove the head. With the head removed, you’ll be able to free the valve more easily, and you can inspect the first two combustion chambers for water indications.

With the head removed, you’ll also be able to determine whether or not you had a hard, brittle asbestos head gasket, and (more importantly) whether the part of the gasket between cylinders one and two came free from the block and head quite easily – while it had to be scraped off the rest of the block with considerably more effort. – Updated: December 4, 2003

The Stevedore is the name of the Atomic 4’s which were shipped into Canada. They are exactly the same as the “regular” Atomic 4, except for a small restrictor ring that was inserted into the inlet of the intake manifold, just above the carburetor mounting flange.

The reason for the restrictor ring was to limit the maximum HP of the engine, so as to comply with Canadian laws regarding the amount of HP (28 – or so) that could be used in sail boats in the 30-foot class. I don’t know what the current situation is with respect to Canadian laws governing the amount of power that can be used in which size of sailboat, but by this time, most of these restrictor rings have been removed from any Stevedore that has found its way back into the US.

In the event that you find this round restrictor ring in the mouth of your intake manifold, you can work it out with a large screwdriver and discard it.

After you remove a Stevedore restrictor, you may or may not notice any difference in performance. The power limitation was most apparent at the very high end of the RPM range of the engine. At RPM below approximately 2500, the restrictor had a minimal effect. – Updated: December 3, 2003

While some manuals specify a rather detailed (and difficult to remember) sequence, we have a rather simple system in our own shops which seems to work very well. We simply start with the center stud and work outward in circular fashion until all studs are torqued.

We do put a great deal of importance on starting at a lower value (we use 25 foot-pounds) for the first trip around the head. We then increase the torque value by 5 foot-pounds on subsequent circular patterns until reaching the factory recommended torque value of 35 foot-pounds.

IMPORTANT NOTE: In discussing torque values with Universal technical service folks many years ago, we were informed that Universal had successfully tested engines with torque values as low as 30 foot-pounds. For this reason, they suggested that if you have any question as to the integrity of the lower threads in any of your studs, you’re probably safer to stop as low as 30 foot-pounds. The concept here seems to be that it is better to have a “solid” 30 foot-pounds on a stud than a “soft” 35.

There is some debate among the experts with whom we network regarding whether or not the torque values were designed with the upper threads of the studs being oiled or dry, the concern being that, if the torque value was designed for dry threads, then the lower friction resulting from oiling them will result in a slightly larger “pull” being applied to the studs at any given torque value.

Our own sense of the oil/dry issue is that you’re probably a bit better off using oil on the threads (the type is not important), simply because it is so difficult in most cases to insure that the threads are “laboratory” perfect. Again, with respect to the above note, if you’re at all concerned over the integrity of the lower threads of a particular stud, stop at a torque value between 30 and 35. – Updated: November 24, 2003

On late model engines, the serial number is on a flat spot in front of a “boss area'” in the casting of the block, directly above the oil fill tube over the flywheel housing.

On early model engines, the serial number is on the front side of the block directly up from the starter. – Updated: November 6, 2003

Most parts are interchangeable between early and late model engines. However, a few parts (particularly some of those used in fuel, ignition, and cooling systems) are unique to early or late models.

If you have an original engine from the mid-seventies or later, with an oil fill tube over the flywheel housing in front of the engine, you can be reasonably sure that your engine will require all late model parts.

If your engine does not have an oil fill tube over the flywheel housing, it may require a mix of late and early model parts. You will therefore need the following information before ordering:

1. To order ignition parts (including the “Ignitor”), you will need to know if your distributor was manufactured by Delco (used on late model engines), or by Prestolite (used on early model engines). Prestolite distributors are distinctively smaller in size, and their condensers are mounted on the outside of the distributor housing.

2. To order cooling system parts, you will need to know if your engine has a thermostat housing (a small dome-shaped casting) located on the front corner of the head, nearest the starter. This thermostat housing would indicate that your engine has a late model cooling system.

3. To order carburetor parts, you will need to know if your carburetor is made of aluminum or cast iron. Aluminum carburetors were used on late model engines. All carburetors were manufactured by Zenith or Bendix, so the manufacturer does not help in determining your carburetor vintage.

4. To order gaskets, you will need to know (1) and (2) above, plus the shape of your transmission cover. Late model engines used a square cover, and early model engines used a rectangular cover with a curved top (“tombstone-shaped”).

– Updated: November 4, 2003

Any troubleshooting situation involves answering 3 basic questions: (1) Does the engine have compression? (2) Does it have spark? and (3) Is it getting fuel? If an engine has those 3 requirements met, it has to run! It might run poorly, depending on its condition, but that is a different matter.

COMPRESSION?
In a troubleshooting context, the easiest thing to do is to remove all 4 spark plugs and hold your thumb over each spark plug hole while your cranking the starter. If you can’t hold the compression back with your thumb, the compression is at least OK. With experience, you can say that compression is poor, normal, or “pretty good”. Here are a few things to consider regarding compression checks:

a. To avoid getting shocked by the spark plug leads, remove the high tension lead from the center of the coil.

b. If you’re by yourself, you can crank the engine from the engine compartment by shorting across the “S” terminal and the large terminal where the battery cable connects to the starter solenoid using a common screw driver.

c. Be sure and close the raw water thru-hull valve on the water intake so as not to flood the exhaust system during cranking and cause water to back up into the engine.

d. Zero compression on one or two nonadjacent cylinders usually means a stuck valve(s). Zero compression on 2 adjacent cylinders usually means a blown head gasket. Zero compression on all four cylinders can mean water has gotten into the inside of your exhaust manifold and has resulted in all four intake valves sticking open. The presence of adequate compression usually confirms the general integrity of the entire mechanical construction of the engine, even to include an open exhaust system.

IGNITION?
With all 4 plugs still removed, reconnect the coil lead to the coil. Hold the other end of the coil lead about 1/2” from the head or block and check for spark while having someone turn the engine over on the starter.

a. The spark may not be as strong as you’d like, and you can’t tell (without further checks) how closely the timing is set to TDC. However, unless the distributor has become loose, it’s not very likely that the timing has shifted enough to keep the engine from running.

b. If there is no spark at all, as in the first attempt to start in the spring, the most likely cause is a thin layer of corrosion over the points which prevents them from making contact and functioning as a switch.

c. If you have any other electrical apparatus connected to the + terminal of the coil (or even the – terminal as in the case of an electrical tachometer), these things all can fail in such a way as to interrupt proper functioning of the coil and should be temporarily removed while you’re doing serious trouble shooting.

FUEL? We’re not talking here about how correct the mixture is, but simply whether or not any fuel is getting to the combustion chambers. The easiest thing to look for is a damp appearance and fuel smell on the spark plugs. A second indication of fuel availability is to remove the flame arrestor and check for some presence of raw fuel in the intake throat of the carburetor. If you have been turning the engine over on the starter for some period of time (especially with the choke pulled) there should be some evidence of raw fuel in the carburetor intake.

NOTE: Some people assume that if there is raw fuel in the intake of the carburetor that the engine is flooded. Because of the updraft design of the carburetor, it is virtually impossible to flood the Atomic 4. In fact, even if there is fuel puddled in the throat of the carburetor, it may still be necessary to choke the engine for a good start. If compression, ignition, and fuel appear to be functional, the problem must be assumed to be intermittent. – Updated: November 4, 2003

If your engine starts and runs fine most of the time, but stops intermittently, it will probably be more difficult to identify the basic system that is failing. For this reason, in the case of intermittent failures, the most important thing on which to focus is learning to interpret the “dying messages” from your engine.

As in developing any new skill, it’s always good to start with something with which you are familiar. In this connection, most people can tell the difference between running out of gas (as in a car), and what would happen if someone accidentally turned off the ignition switch.

Running out of fuel usually results in a rather “soft and gentle” shut-down. Small missing sensations may be noticed that gradually get worse until the engine finally stops.

If the ignition switch were inadvertently turned off, the shut-down would be very sudden – perhaps even “startling”.

These first two messages from your engine would then be very different:

1) Message one: “I’m starving for fuel”.

2) Or message two: “My spark stopped suddenly as if my primary ignition circuit opened up” (which would feel the same to the engine as if someone really had turned off the ignition key).

Familiar causes of fuel starvation include dirt in the carburetor, clogged fuel tank vent line, faulty fuel pump (or electrical connections in the case of electric pumps), clogged filters, etc.

If the “dying message” drags on long enough, you can try pulling on about half choke before the engine quits completely. If you can affect the engine performance (even a little bit) with the choke, it is good confirmation that you¹re correctly hearing a “fuel starvation message”.

If the message continues to indicate that some one inadvertently turned off the ignition switch, the likely cause of the shut down is an open circuit somewhere in the primary ignition system – frequently in the boat’s circuitry.

IMPORTANT NOTE: During most troubleshooting work, it is frequently necessary to turn the engine over on the starter with the engine NOT STARTING. Be sure to close the raw water thru-hull valve during these times so as to avoid filling the exhaust system with raw water until it backs up into the exhaust manifold, and into the combustion chambers of the engine.

To confirm an ignition failure message, remove the coil lead (the high tension one) from the center terminal of the distributor cap as soon as possible after shut-down, and hold the end of the lead close to the block or head (about 3/8″ away). Check for spark between the coil lead and head as you turn the engine over on the starter.

If you see no spark, refer to the troubleshooting section of Chapter 3 of the Service Manual.

NOTE: Remember that many faulty connections within the primary ignition system will work after they cool – usually within a half an hour or so. Therefore, even if you do see a spark in the preceding step, don’t completely abandon your first assessment that the problem may be in the ignition system.

If preliminary checks of the fuel system indicate that the engine is in fact getting fuel, it would be a good idea to perform a few ignition checks. Faulty connections within the boat’s primary ignition circuit are particularly hard to pin down. It is frequently necessary to install a “diagnostic” jumper wire between the coil (positive terminal) and the positive battery cable at the starter solenoid. If the intermittent shut-downs cease, you’ve confirmed that the problem is somewhere in the boat’s ignition system.

Another distinguishing feature of a shut-down could be that it is neither soft nor sudden, but that it hesitates (stopping and starting) sharply in an almost aggravating way. The engine may even back-fire or “pop” a bit in this mode.

This third dying message would be rather specific:

3) “My coil is breaking down when it gets hot”, or “My condenser worked loose on its mount, or “There’s a very loose connection somewhere in my primary ignition circuit” (possibly an intermittent short to ground). These messages frequently suggest that the problem is heat related.

A fourth distinguishing feature (fortunately extremely rare) is that the shut-down may be accompanied by signs of mechanical failure: i.e. loud noises, loss of oil pressure, severe overheating, etc.

The message here would be quite clear:

4) “Help, I’m self destructing!”

In addition to the foregoing specific messages, there are, what may be called, “near-death experiences” which are also important in clarifying which of the preceding four messages the engine is sending:

1) Do the shut-downs repeat at some predictable time interval? And, is it possible to restart the engine after some predictable interval of time following a shut-down?

These observations would suggest that the shut-downs are heat related and would relate to message 3, or possibly resulting from a partial vacuum in the fuel tank (from a clogged vent line). This last condition would relate back to message 1.

2) Do shut-downs occur during some predictable operating condition? This observation would suggest a sticky float valve in the carburetor, although this is not a common problem.

And finally, in a different context completely, there is my favorite question: Have you performed any maintenance on the engine recently? It always provides me with a bit of tension releasing amusement when I’m told: “Why yes, I just replaced the plugs, points, and condenser last week, – so I know that the problem can’t be in that area!” (Not necessarily so)! Whenever you experience problems after performing maintenance, always go back over every step of your work to see if you overlooked something. This is one of the most fertile places to find reasons for intermittent shutdowns. – Updated: November 4, 2003

This condition is usually the result of low power caused by something that was done incorrectly during recent engine maintenance. The reason the engine seems to run better in reverse is because the reverse mode has a 1.27 to 1 gear reduction. Here are some examples of maintenance problems that we’ve heard about:

Three to five times each year, spark plug leads were found to be installed in an improper sequence following a tune up! Cylinders 2 and 3 can apparently be reversed, and the engine will run fairly well in neutral, but will have practically no power in forward. According to one caller, his plug wires were reversed for an entire season before he found the cause of his power loss.

Another recent maintenance “oops” involved a minor repair of the exhaust system which required that the manifold be removed. On reinstallation, the old gasket was improperly installed, resulting in intake leaks and very poor power under load.

Assuming that there was absolutely nothing done to the engine since it was last running OK, check the following areas for potential problems:

1) Check for something hanging on to the prop.

2) Check basic integrity of the engine by a quick compression check. For the purpose of diagnosing a major power loss, a simple check using your thumb over each spark plug hole is more than adequate. If your compression is sufficient so as to make it impossible for you to hold your thumb over each spark plug hole while cranking the engine with the starter, the cause of your power loss is not a major mechanical failure. If compression is weak in two adjacent cylinders, or water is observed in any of the combustion chambers, the head gasket has probably failed. If compression is “zero” in any of the cylinders, a valve has probably stuck open. If you are using a compression gauge, compression values over 80 psi are considered adequate.

3) Check for proper carburetor function. Normally, an Atomic 4 will accelerate almost “explosively” as you flick the throttle forward. If there is any hesitation or mild backfiring, a lean condition caused by dirt in the main jet is the most frequent cause. In most cases, a problem related to a fuel issue will manifest itself in neutral as well as in forward, but in mild cases, a lean condition might be missed in neutral, but will surely show up under load.

4) Check for proper ignition. As in the case of subtle lean fuel mixtures, there are subtle ignition problems that can show up under load but not necessarily in neutral. In this category, plug condition is the best indicator. If one plug is noticeably blacker (or oilier) than the rest, look for the relatively few things that can affect only one plug, such as the plug itself, the plug lead, or a cracked distributor cap. If all the plugs are badly fouled, check things that can affect all plugs, such as a loose condenser, badly worn points, shorting coil (or oil leaking from the coil), cracked distributor cap, or a bad coil lead. – Updated: November 4, 2003

The causes of poor acceleration are almost always found within the carburetor. An easy way to confirm a carburetor problem is to pull the choke control until the choke is approximating half-closed. If acceleration improves (even slightly) the problem is almost certainly within the carburetor, and it will probably need a good cleaning.

If the hesitation is just as the RPM is coming off idle, and the engine then accelerates quite normally, the problem is most likely a blockage in one or both of the tiny idle ports in the body of the carburetor just off to the side of the throttle valve (near the top of the carburetor).

If the poor acceleration continues throughout the entire RPM range, the problem is most likely a partial blockage within the main jet.

If the problem cannot be found within the carburetor, there could be something more serious happening within the engine, causing it to lose compression in one or more cylinders. This possibility can easily be investigated by removing the plugs and checking for adequate compression by holding your thumb over each hole as you have someone crank the starter a few turns. Adequate (or functional) compression means that the compression is sufficient to make it practically impossible to hold your thumb over the spark plug holes while the engine is being cranked.

IMPORTANT NOTE: Be sure to close the raw water thru hull valve anytime that the engine is being cranked without the intention to start it. In many boats, the amount of cranking required by a compression check is sufficient to cause water from the engine driven pump to flow through the engine, filling the exhaust system with water until it backs up into the engine through the exhaust manifold. – Updated: November 4, 2003

There is no sure way to relate your serial number to a particular engine manufacturing date. However, there are certain features that you can use to identify the latest engines: The very late group of engines (circa late 70’s) had flat sheet metal flywheel covers. These engines generally had serial numbers starting around 190,000. The very latest engines (circa early 80’s) came with electric fuel pumps, and the blocks of these engines were no longer drilled to accommodate the small push/pull rods used to operate mechanical pumps. You would, of course, need to remove the electric fuel pump mounting bracket to determine whether or not your block had this hole drilled into it. The serial numbers of these engines generally started around 200,000.

The only other way to approximate the date of an engine is to check the manufacturing date stamped onto the carburetor side of the block. Unfortunately, this date only applies to the date of the block. In many cases, blocks didn’t find their way into an engine for several years. – Updated: November 4, 2003

Marine surveyors often refuse to make any evaluations regarding the engines. On the bright side, it is clear from our own customer feedback that there are many more well maintained Atomic 4’s in today’s market than there were ten years ago, and many of these engines are fresh water cooled. In the early 90’s, the majority of our first-time callers reported that they just bought a boat with a “basket-case” Atomic 4, and they had to spend the next year bringing the engine back to health. Today, at least half of our new owners are simply calling for parts or advice on how to best maintain their well-running engines.

Here are a few things that you can look for:

1) It is obviously very important to check on the maintenance history of the engine if one is available. The maintenance history, along with the ability to talk with the prior owner, can add insight to the findings of the following checks.

2) Check the exterior of the engine for signs of deep rust or scaling. Be especially critical of the alternator side of the block. In some cases, seals around water jacket side plates develop leaks, and given the limited access to that side of the engine on many boats, these leaks can go undetected for long periods of time, and deep scaling can result. In a few cases (fortunately very few), blocks have had to be scrapped due to this scaling extending all the way through the block and into the crankcase.

3) The engine should be started and brought to a normal operating temperature of 160 to 170 degrees for raw water cooled engines, and approximately 180 to 190 degrees for fresh water cooled engines. It is best to run the engine in “forward” and under load. If you are checking the engine in the slip, it’s OK to simply pull against the dock lines. Check for any unusual noises. Atomic 4’s are known for running rather quietly and smoothly.

4) Check for fluid leaks. Be especially critical of any evidence of gasoline around the carburetor or fuel lines.

5) Check for normal oil pressure of 30 to 40 psi by around 1500 RPM and 20 psi, or above, at idle.

6) Run the engine for a short time at maximum power to check for any unusual sounds, excessive smoke out of the exhaust, or fumes from blow-by in the cabin.

7) In neutral, the engine should accelerate quickly as you flick the throttle from idle to full throttle without hesitation. It’s important that you do not allow the engine to actually reach full RPM during this check. This is simply an acceleration check. The RPM never needs to go much above 2000.

8) Shut the engine down and check the compression as soon as you can remove the spark plugs without burning your fingers. The combustion chamber volume in the heads of in-service Atomic 4’s vary considerably, and compression can therefore vary from as low as 85 psi to as high as 120 psi, with the average being around 100 psi. Compression readings should have a maximum spread within 5 or 10 psi.

9) While the spark plugs are removed, check for excessive carbon build-up or oiliness. Do not be too critical of a black velvet sootiness as long as the plugs are dry.

If you are buying a boat without the opportunity to actually run the engine, perform as many of these checks as possible.

1) With a cold engine, compression readings can be expected to vary much more than in a warm engine, and if the engine has not been run in quite a while, valves might be a bit sticky, which will affect compression. These conditions are frequently not serious, and will clear up after the engine is started and given a Marvel Mystery Oil treatment (5 or 6 squirts of oil in each spark plug hole).

2) With the spark plugs removed, run the engine on the starter and check for oil pressure. Oil pressure at starter RPM will usually be around 20 psi. – Updated: November 15, 2003

Speaking as a survivor from the “old days”, I’ve heard a lot of war stories about hand cranking myself, but I have never had much problem cranking engines whenever I had to do so (including the Atomic 4).

Be sure that the end of the crankshaft and the roll pin itself are relatively clean and free from burrs, etc. Then check the end of the crank for the same good condition, and I would recommend putting a little grease on the end of the crankshaft and crank. These precautions will ensure that the crank will pop right off the end of the crank as soon as the engine starts.

If the batteries are any good at all, engines will usually start amazingly well, due to the fact that the starter is not draining 800 to 1000 amps of power away from the coil. It’s best to have a person in the cockpit to work the choke and throttle, just as if you were using the starter.

The Atomic 4 is rather gentle to start, and backfires are rare, especially if you use full choke so as to avoid a lean start. As with any other skill, it is good to practice a few times before you are actually in position to have to use the crank.

You need a minimum of 7 1/2” from the center of the crankshaft to swing the crank for timing the engine, etc., but you ought to have at least 9” for using the crank for actual starting of the engine (for safe knuckle clearance). – Updated: November 4, 2003

Whenever an Atomic-4 starts hard, but then runs OK after it starts, it is almost always the case that the choke is not closing completely, and/or a person’s starting technique itself is less than perfect.

Due to the updraft design of the carburetor, the engine relies on a spring-loaded poppet valve on the choke disk to allow just the right amount of air to be drawn in through a completely closed choke valve for a good crisp start. If the choke valve is open even a slight bit, hard starting will almost surely result.

Your choke cable should pull almost effortlessly, so that the resistance you eventually feel as you continue to pull the the choke knob is in fact the choke valve itself closing. If you’re feeling a lot of resistance within the cable, you’ll run the risk of not quite getting the choke valve completely closed, or you may actually damage the choke assembly on the carburetor by pulling too hard on the choke lever after the choke is closed.

It is well to point out here that it’s almost impossible to flood the Atomic 4. Even if fuel is seen to be pooling in the mouth of carburetor, the choke must be fully closed for a good clean start.

Here are a few tips on starting technique:

1) “Pumping the throttle” is totally ineffective as a starting technique for the Atomic-4. Since there is no accelerator pump within the carburetor, pumping the throttle has absolutely no effect on anything in terms of supplying more or less fuel to the engine.

2) If your engine tries to start, but falters and stops as soon as you stop cranking on the starter, it is likely simply not getting enough fuel to work itself out of the idle range and into the lower range of the main discharge nozzle of the carburetor (which occurs around 1000 RPM). After an engine is warmed up, it will tend to start OK in idle, but cold engines seldom will start and run within the idle range. They need to start and warm up in the lower range of the main discharge nozzle before they can be brought back to idle.

3) The best setting for the throttle during starting is solidly off of the idle stop, so as to uncover both idle ports and get you into the “off idle” range of operation. It’s somewhat better to err on the high side in terms of throttle setting. If your engine ends up racing the instant that it starts, you can back off a little on the throttle setting during future starts. – Updated: January 3, 2004

Assuming that the previous owner followed the simple procedure of “fogging” the engine with Marvel Mystery Oil when it was last shut down, and/or that the engine still turns freely, there are only a few things that you need to be concerned about.

1) During early attempts to start, we recommend keeping the raw water thru hull valve closed until the engine actually starts, to insure that you won’t flood the exhaust system (and engine) with water. As soon as the engine does start however, be sure that you open the valve immediately.

2) Remove the spark plugs and turn the engine over a few times on the starter to check for compression. The compression should be enough so as to make it practically impossible to hold your thumb over the each of the spark plug holes while the engine is turning over. If one of two cylinders are weak, it might be that one of the valves is slightly hanging up. This condition will probably clear up as soon as the engine starts. A few squirts of Marvel Mystery Oil in the weak cylinders would be helpful.

3) Check all fuel filters, and inspect the fuel supply by removing one of the plugs in the bottom of the carburetor (preferably the “main passage plug”). Then pump some fuel through the carburetor and into a small glass container, by either working the manual priming lever on the mechanical fuel pump, or by powering the electrical fuel pump.

If the fuel appears clean and free of water, reprime the carburetor, and inspect the choke valve to insure that it fully closes when you pull the choke control in the cockpit. You should then be ready to start, fuel-wise.

NOTE: There is frequently a lot of concern over old fuel. If later, the engine won’t start and you think that it is due to old fuel (like if it smells funny and has a strange color), I would suggest that you pump off enough to try it in a lawn mower or other small engine prior to going through the rigors of draining and replacing all the fuel. Not that you may not want to do a lot of heavy maintenance on the fuel supply at some point, but you can probably pick a better time when you’re dealing with a lot of other start-up issues. In most cases, the concern over old fuel is overstated.

4) Clean the points by rotating the engine until they are closed, and then run a piece of cardboard between them. Then, with the ignition switch on, flick the points open and closed a few times while holding the main coil lead from the top of the coil about a quarter of an inch from the head, while observing for a good spark. If the spark is healthy (a half inch or better), the engine should be ready to start, ignition-wise.

5) Check for good oil in the crankcase, charge the batteries, and start the engine. – Updated: November 4, 2003

here are several methods of dealing with studs which will no longer hold proper torque, depending on how badly the threads in the block are damaged:

1) If you stop torquing as soon as a particular hole starts to feel “soft”, you could re-tap to 10 mm coarse threads and install one of our 10mm head studs. The 10mm tap is the largest tap that will go through the original holes in head, which means that this technique could be used without removing the head. Our 10mm studs are machined so as to retain 3/8″ fine threads on the upper end.

2) Unfortunately, by the time a stud is felt to be failing, it is usually too late for the 10mm solution. In these cases, it is necessary to remove the head and re-tap the failed holes to 1/2″ by 13 (coarse threads), and to then install one of our thread repair bushings (product number OBLK_09_114).

NOTE: See below for “text-only” instructions to assist in installing these bushings.

3) Helicoils can be used in place of solid repair bushings; however, it is somewhat more difficult to seal the “coil” design of Helicoils and prevent water from the cooling jacket from working up past the threads of the studs.

4) Some folks have drilled out the holes in the head so as to accommodate the use of 7/16″ studs. While I have no serious issues with this practice, we have no data on how to adjust the torque value for the larger thread diameter, nor do we have any source for appropriate 7/16″ studs.

5) As a final thought on this subject, it’s very important to thoroughly inspect the threads in stud holes prior to assembly (an ounce of prevention is worth a pound of cure). In the case of holes in which the threads are observed to be effected by corrosion, damaged by over torquing, or simply exhibit a “sloppy” feel, we recommend the use of JB Weld to give the threads a little additional strength, and then (in the case of heads) only torquing the nuts to 30 or 32 foot-pounds – even the ones which were not suspect.

Universal technical folks have told us some years ago that they have considerable test data which show that 30 foot-pounds of torque on head studs retains a good safety margin.

INSTRUCTIONS FOR INSTALLING REPAIR BUSHINGS:

1) Drill out the failed hole(s) to 7/16″, then tap for 1/2″ X 13 (coarse) threads. It’s critically important to keep the tap straight as you work. A small carpenter square is helpful. It’s usually possible to “adjust” the tap as you go, in the event that you discover it is leaning a bit one way or the other.

2) Thread the bushing onto the end of a new stud, and dry run it into the hole a few times. You can double-nut the stud to make it easier to turn it in, but be very careful to not get the bushing stuck in the hole at this point. If it gets tight at all, go back in with the 7/16″ drill and “worry” the hole a bit larger by wobbling the drill a small amount. Continue to check the bushing for fit, and when you can install it almost all the way in using your fingers, you’re ready for the next step.

3) Smear some JB Weld around the outside of the bushing and around the inside of the hole in the block.

4) Turn the bushing in using a wrench on the double-nuts until only the small round shoulder is exposed outside the hole.

5) The bushings have 4 small slides around the outside, which get tapped in between the bushing and the block after the bushing is finally set in place to keep it from turning. Don’t worry if one (or even two) of these slides breaks off. Any two slides should hold it in place while you remove the stud.

6) Grind, or file, the top of the bushing flush with the surface of the block. If you can get your hands on a small hand-held grinder, it makes this part of the job much easier.

7) It’s best to dry run the head or manifold over all of the studs before the JB Weld has had a chance to set up. It is sort of a good thing if your bushing ends up having a small bit of wobble, so that if the stud is just a bit less than perfectly straight, the head or manifold can bring it into alignment. You can even install the nuts, but only hand-tighten them until the JB Weld has had a chance to fully cure (usually overnight). – Updated: November 6, 2003

The practice of using bolts instead of studs puts considerably more stress on the threads in the block.

The explanation centers around the fact that studs impose a straight-line pull on the threads in the block, as the nuts are torqued on the upper threads. By contrast, bolts “grind” into the threads in the block as the bolts are tightened and torqued. The threads in the block will seldom tolerate more than one or two “torquings” of bolts before failing.

There is also a problem with the effectiveness of the torquing process itself. Due to the steeper slope of the coarse threads on the bolts, a torque value of 35 foot-pounds will result in less downward force on the head than will the shallower slope of the 3/8″ fine threads in the upper end of the studs. Happily, there seems to be enough safety margin in the torque value itself, so that problems related to under torquing seldom manifest. – Updated: November 6, 2003

Unfortunately, such a sound is almost always a failed rod bearing. It is sometimes accompanied by a loss of oil pressure, but by no means in every case.

The knocking sound from a rod bearing in early stages of failure will usually change rather profoundly as engine RPM is raised and lowered from idle to just above idle, and in some cases, the knocking sound can be made to disappear completely by RPM changes.

As the failure progresses, however, the sound will get much worse and eventually be very constant. The only cure for failed rod bearings is to remove the engine for a major overhaul. – Updated: November 4, 2003

This sound is most likely nothing more than a valve tap from one or more valves. The Atomic 4 has mechanical valve tappets, and when the clearances are set conservatively to the specified gaps of .010” and .012” for intake and exhaust valves (meaning on the loose side), there will be an occasional clicking or tapping sound heard. These sounds should reduce when the engine is fully warmed up, and should not be heard at normal cruising RPM. In short, we consider a slight valve tap at idle to be a relatively “healthy” sound. It should also be pointed out here that the Atomic 4 has a very reliable history in terms of valve and valve seat wear. In spite of widespread concern over the effects of using lead-free gas, we have never seen any indication of valve seat damage (“peening”) as a result of lead-free gas, even in engines with regular cast iron seats. Use of Marvel Mystery Oil in the fuel tank (6 to 8 ounces per 10 gallons) is very effective in keeping valves working freely and reliably. – Updated: November 4, 2003

Catalina 30 has a very long wiring harness which contains three quick disconnects. I would start by inspecting each of those disconnects for corrosion, etc. There is one disconnect at each end of the harness (at the engine and at the instrument panel), and one under the cabin sole just in front of the galley sink which you can access through the same panel you lift up to service the stuffing box.

The primary circuit goes through this harness, and if any of the quick disconnects are making a poor connection, the engine will shut down as if someone turned off the ignition switch. The nature of this problem is that it can be very intermittent, meaning that you might be able to see a spark at the moment you are checking the plugs while cranking, but not be getting enough of a reliable spark for normal engine operation. – Updated: November 4, 2003

Your symptoms are very consistent with a head gasket failure.

Two important questions are: What is the compression in the two failed cylinders, and are the failed cylinders side by side? Poor compression in two adjacent cylinders would tend to confirm a head gasket failure between those two cylinders.

If you do not have a compression gauge handy, you can simply hold your thumb over the two spark plug holes. If you can resist the compression by holding your thumb against the holes while someone cranks the engine over on the starter, a head gasket failure would be the likely cause. – Updated: November 4, 2003

With compression, fuel, ignition all OK, the engine has to start.

It may be that your choke is not closing completely. Due to the updraft design of the carburetor, the choke must close completely so that the poppet valve in the choke valve can provide the correct fuel mixture.

If I were on your boat, I’d remove the flame arrestor and look up the throat of the carburetor. If the choke is working and the carburetor and fuel supply is in fact OK, there should be raw fuel puddled in the bottom of the carburetor intake throat after 10 to 15 seconds of cranking. If the intake throat is dry (after that amount of cranking), there is a problem with the carburetor.

If there is fuel puddled in the bottom of the carburetor, then the engine is not starting due to some problem in the ignition system. If you are getting a good secondary discharge out of the coil, then it may be that the engine is out of time. This would be a good guess in the event that someone worked on the engine lately. – Updated: November 6, 2003

Based on the original design compression ratio of 6.3 to 1, the compression would be 95 PSI. In fact, original test data recorded compression values very close to this value. However, most in-service engines will have average compression readings of 100 to 115 PSI. There are several reasons why compression is usually higher than the design specification: 1) carbon buildup in the cylinders, 2) heads being milled, or the use of only one head gasket during overhaul, and 3) variations in combustion chamber depths within cylinder heads. NOTE: While Universal never officially changed the specification for the depth of combustion chambers in cylinder heads, many of the later engines (circa late 70’s and early 80’s) have considerably shallower combustion chambers than earlier heads. Fortunately, new heads sold today (both our aftermarket heads and the more expensive heads sold by Westerbeke) have combustion chambers of the original depth. It’s important to point out that since the Atomic 4 is a low compression engine by design, performance does not seem to improve by artificially increasing the compression ratio above the design specification of 6.3 to 1. – Updated: December 6, 2003