Surveying an Atomic 4

[dwight yachuk]

Hi,

I'm off to have a look at a /columbia 36, circa 1968, with its original atomic 4. The owner says it runs great and has never been a problem.

Is there a survey checklist available of the things I should look at when checking the atomic 4 engine?

dwight yachuk

(future A4 parts buyer)

[Don Moyer]

Dwight,

Here are a few things that you can look for:

1) It's 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 scraped 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 4s varies 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 buildup 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 the above checks as possible, plus the following:

1) 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.

2) Check the compression. 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).

Best regards,

Don Moyer

[dwight yachuk]

Thanks a bunch Don,

We'll be able to run the engine as well as take her out for a sea trial. From literature I've read it's suggested to leave the engine running (in neutral) even when under sail during the sea trial. Would you agree with that?

Is Marvel Mystery Oil available at most chandleries? The boat is in in Port Clinton Ohio.

I'll have to find someone to do a compression check as I don't have the tools nor experience to do this.

The boat has been on the hard for two years. I'm assuming the gas was either drained or has evaporated. I know that diesel slug and bacterial growth is a problem but I don't know about gasoline. Is there a concern with old fuel, sludge in the tank, lines?

I plan to replace the spark plugs (er, how many are there? ) and fuel filter(s). Any suggestions on which spark plugs and which fuel filters to use?

Thanks for all this great help. Once I know more about the engine (in the fall perhaps), I'll contact you about the various upgrades I've read about here.

dwight yachuk

[dwight yachuk]

PS

I notice you have a service and overhaul manual. If the present owner doesn't have one I'll order it pronto.

dwight

[Don Moyer]

Dwight,

Answers to your new questions:

1) From literature I've read it's suggested to leave the engine running (in neutral) even when under sail during the sea trial. Would you agree with that?

Not really. I don't know of any good reason to let the engine run in neutral, unless you're afraid that the engine might not start if you shut it down.

2) Is Marvel Mystery Oil available at most chandleries? Most probably.

Best regards,

Don