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Discussion Starter #1
Been having engine trouble and just was "informed" by the marina that I have lost close to half of the compression in all 4 cylinders. They were pretty vague about the possible causes and related repair costs. They did warn about sinking too much $ trying to trouble shoot.

Any body have any suggestions?

Not really thrilled about the prospect of buying and installing a refurb for what I understand could be upwards of $5K.

New to the whole arena and could use any help I can get.

Thanks.
 

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First of all, a 'compression test' without a dry reading versus a 'wet' (a wee bit of oil dumped into the combustion chamber) is next to worthless .... WHAT were the compression values or does this require an additional charge for such an answer? WHAT was the engine temperature when the 'readings' were taken? When was the compression gage last 'calibrated' ???????
A 'dry' reading will indicate the integrity of the head/valves; a 'wet' reading will show the integrity of the piston rings, etc.
That your marina didnt report such would make me VERY suspicious that they are simply looking to do a 'replacement' ($$$$$$$$).

If the cylinder pressure are 'equal', the engine is still 'operable'.
Id strongly suggest that you get yourself a compression gage and learn to do such simple testing. yourself .... (wet and dry). NAPA and other national, etc. 'auto stores' sell compression gages at very reasonable cost ... and they come with 'instructions'.

Go to Moyer Marine Atomic 4 Engine Rebuilding and Parts and join the forum there. Also you can purchase Don Moyer's "Atomic-4 ... Rebuild and Maintenance Manual" ... and save yourself a fortune when dealing with 'marinas' looking to do unneeded work at well beyond outrageous prices- and to better guard yourself from unscrupulous 'shysters'.
 

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Discussion Starter #3
I did not know enough to ask these questions.
They did indicate the cylinder readings were between 30 and 50 (not all the same) and that 90 is what I should be getting.
The motor worked perfectly about6 weeks ago, and then again about two weeks ago for about 15 minutes.
I will check out Moyermarine.
Thanks.
 

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Tartan 27' owner
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What RichH said times 10.

The Atomic 4 is a great auxiliary engine for most purposes. Most marinas can't or will not work on them and will charge you around $80/hour if they do. They are much more likely to tell you it is 'done' to get you to install a diesel which they will likely service as well. You can do most (if not all) of the service on this engine yourself and save a boatload of bucks in the process.
When we got our boat with A4 about 8 years ago I knew almost nothing about the engine. I have learned quite a lot since then and I am now moderately capable of doing all or most of the work it needs. The Moyer Marine forums even Don Moyer himself are great resources to help get you through any 'challenges' you might encounter.
At a minimum you should know how to replace the ignition components (spark plugs, wires, distributor, rotor etc.), change the oil, clean the carburetor, change water pump impeller etc. If I had to pay a mechanic to do these items I could not afford my boat.

Post your question over at the Moyer website for additional encouragement.
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If the motor was working perfectly both six and two weeks ago, what trouble were you having and when?

edit: in other words, its hard to advise you to buy a tester and do a compression test at all.
 

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Additionally, there are a few good mechanics who will work on these engines but since your profile does not indicate your location it would be difficult to make a recommendation.
Most marinas just see you as their next cash cow and will tell you anything to get you to go for a diesel conversion (try more like $12k - $16K).
I have seen working (replacement) A4's listed for sale for <= $2K (about $4K if you get a rebuilt engine from Moyer).
 

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First of all, a 'compression test' without a dry reading versus a 'wet' (a wee bit of oil dumped into the combustion chamber) is next to worthless .... WHAT were the compression values or does this require an additional charge for such an answer? WHAT was the engine temperature when the 'readings' were taken? When was the compression gage last 'calibrated' ???????
A 'dry' reading will indicate the integrity of the head/valves; a 'wet' reading will show the integrity of the piston rings, etc.
That your marina didnt report such would make me VERY suspicious that they are simply looking to do a 'replacement' ($$$$$$$$).

If the cylinder pressure are 'equal', the engine is still 'operable'.
Id strongly suggest that you get yourself a compression gage and learn to do such simple testing. yourself .... (wet and dry). NAPA and other national, etc. 'auto stores' sell compression gages at very reasonable cost ... and they come with 'instructions'.

Go to Moyer Marine Atomic 4 Engine Rebuilding and Parts and join the forum there. Also you can purchase Don Moyer's "Atomic-4 ... Rebuild and Maintenance Manual" ... and save yourself a fortune when dealing with 'marinas' looking to do unneeded work at well beyond outrageous prices- and to better guard yourself from unscrupulous 'shysters'.
The above is truth. A steel sleeve has a different expansion coefficient than the aluminum piston contained within. Aluminum takes on heat initially much faster. If the compression is even all of the way across and it ran last week. It shall run again! I think MacArthur said that when coming back to the PI.
 

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Well

The correct thing to do is a leak-down test as you will find the extent and location of the problem cranking speed alone has a huge influence on compression tests

Engine Leakdown Test

Hearing Problems
Beyond getting an overall picture of engine condition, the leakdown test is an excellent way to pinpoint where engine problems are before tearing down the engine. Listening for where the air is escaping by ear can isolate the problem.

Intake Valve: Air whistling out of the intake, carburetor, or throttle body indicates leak at the intake valve.

Exhaust Valve: Air heard hissing out of the tailpipe, turbocharger, or exhaust manifold means an exhaust valve leak.

Piston Rings: Whistling or hissing out of the PCV valve, oil filler cap hole, or dipstick tube means the air is pushing past the rings. Suspect ring or cylinder wall wear.

Head Gasket: Air bubbles in engine coolant seen at the radiator filler cap could mean air escaping into the coolant past the head gasket.

Cracked Cylinder Head: Bubbles in coolant or coolant being pushed up out of the radiator neck can also indicate cracks in the cylinder head or cylinder wall


From what i have seen and A4 can be run pretty far into the ground and more or less just reach a its NOT gonna run anymore point as for example mine came with a 40 year old distributor cap :eek:
 

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"Been having engine trouble" What kind of trouble? Could be fuel delivery or ignition problems which would have no relation to compression. Unless you have a blown or leaky head gasket compression loss would probably happen over a fairly long time. As the engine was running fine before the trouble I suggest you go slowly and check the small items carefully before you open it up. Let us know what you find.

Dabnis
 

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Hackettsan -
Perhaps you could itemize the signs and symptoms of your 'problem' ... and we can collectively brainstorm from there.
 

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Discussion Starter #11
First of all I should say she's a 1976 (Housed in a great C&C 27 Mark II).
I should also mention I don't get out there enough and she sits for over a month at atime sometimes (two little kids).

I had a fuel pump replace at the beginning of the season and, after a subsequent throttle adjustment, she was running great.

Two weeks a go she stalled while idling (I was re-rigging after hurricane Irene). I was able to get her started once or twice for less than a minute. The only non working gauge on the boat is the fuel gauge. I optimistically thought Maybe I was out of fuel. A few days later I filled her up (I was not on E after all). Also got her started a couple of times, but if I did not rev the throttle she stalled. Eventually she wouldn't start at all and I asked the marina to check it out as they had done the Spring tune up and the fuel pump replacement in June.

They told me I had varying degrees of compression loss in all four cylinders.
Trying to get anything else out of them is like pulling teeth.

This is my first full season, and it has been a tough one!
 

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Several things to check:

Carburetor fouled ... typically dirt/gum deposits on the carburetors 'emulsion tube'. The emulsion tube is a thin hollow tube with teeny holes. The emulsion tube controls the air/fuel ratio. Any dirt in or on the 'holes' will cause the air/fuel ratio to vary - very common ailment with this updraft carburetor; easy fix - just disassemble and inspect/clean. A gasoline filter housing that is supplying fuel to the carburetor and is 'rusting' in the bottom of the bowl section will usually be the cause of dirt, etc. catching on/in the small 'holes' in the emulsion tube. The emulsion tube is a quite precision device and needs to be 'perfectly clean'.

The A4 is a quite low compression ratio engine and will run adequately at idle even with compression issues and will 'run' with only 2 or 3 cylinders 'operating'. However, ......
A. Head gasket leakage. The usual leak occurs between cylinders #3 & #4 and involves cross cylinder leakage as well as water leakage. The head should be periodically retorqued. One of the symptoms of a head gasket being 'blown' is the engine will idle quite well but as soon as throttle/load is applied, the engine stalls out.
B. Sticky exhaust valves ... depending on the configuration of the wet exhaust system, high humidity in the exhaust circuit can cause the stems of the exhaust valves to begin to rust; the rusts causing friction which leaves the exhaust valve either non-moving or partly closing (reduced compression value/reading). Easy assay and 'fix': open the valve cover on the side of the engine, disconnect the main high tension wire between the ignition coil and the distributor cap to insure that the engine will not 'start', spin the starter as you WATCH the exhaust valves go 'up and down'. If a valve is fopund to be sticking - remove spark plug, 'go into' the combustion chamber with a 'bent' screwdriver (the valves are on the portside of cylinders) and PUSH the offending valve down so that its fully seated ... then spray the valve stem with an anti-rust compound such as "PB
Blaster", etc. let soak a bit, then spin the starter and spray the valve stem until 'repolished' and free of rust .... and the valve 'reliably' returns to 'full stroke'. Sticky exhaust valves are quite common on A4s that 'sit' for long periods ... the cause is usually a pin hole that develops between the gas and water side of the exhaust manifold. A pressure check by blocking one 'end' of the water port or the manifold and applying 40-60 psi water pressure on the water circuit will prove/disprove any 'pin holes': apply water pressure, close the water supply and look for a drop in a gage pressure that is applied to the water supply, etc. Such can be 'brazed' closed.

Get Moyer's "Rebuild and Maintenance Manual" ... and visit the Moyer forum. A4s simply dont 'wear out' they can run almost forever ... the usual thing that kills an A4 is internal rusting of the block and Moyers Manual will describe simple testing that will determine if there is enough 'meat' still left on the inside of the engine. Usually if there enough meat / wall thickness left then the engine can be easily rebuilt, repaired etc.
 

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A 1976 Atomic four is a relatively new engine by A4 standards. Mine is from 1967 and still works reasonably well but needs TLC now and again.
I know of a good mechanic near Annapolis, MD but so far I only know you were hiding from hurricane Irene like the rest of us on the east coast from NC to ME.
Your starting and idling problems could be related to a number of causes: distributor timing, incorrect plug sequence to sparks, corroded spark plugs, stuck float valve in carburetor etc. If the new fuel pump they installed was electric there could be a bad oil pressure cutoff switch which would not allow the pump to pump fuel.
What you can do now is to inspect your spark plugs. Once the plugs are out you can squirt or spray some Marvel Mystery Oil in each cylinder (< 1 oz). The MMO should help lubricate the piston rings and valves.
What was wrong with the old fuel pump that was replaced in June and was the old pump the mechanical or electric kind?
 

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mmmmmm new elec. fuel pump .......
With an electronic fuel pump, there is usually (and should be) a fuel safety cut-off switch that monitors the OIL PRESSURE. If (due to accident, etc.) the oil pressure drops or the engine stops ... the drop in oil pressure will de-energize the 'switch' and automatically shut off the fuel pump.
If there is insufficient oil pressure to open the safety switch with the starter engaged and thus allow the fuel pump to begin 'pumping' ..... the fuel pump will not deliver fuel and the engine will not start. There should be a 'jumper' switch across the safety switch so that you can energize the fuel pump during/before starting and the engine is not delivering sufficient oil pressure.
BTW if you use a double pole (STDP) switch, this becomes a good anti-theft device ..... center tap = 12vdc, one end tap - fuel pump 'jumper', other end tap - not connected (open short) thus 0 volts to pump.
 

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Lots of good info in this thread. Definitely go to the Moyer forum and discuss this.

But first of all, the A-4 is a low compression engine to begin with, and everything about it is heavy duty. That's what makes them so robust.

The stalling symptoms you describe don't seem to be compression related. An engine with relatively even compression across all cylinders, will run even if the compression isn't optimal. It sounds to me like the marina did a dry compression test and stopped investigating.

Your symptoms seem more fuel or electrical related. It could be a variety of inexpensive, and simple things:

Ignition points worn out, and/or mis-adjusted.
Condensor worn and failing.
Primary ignition coil failing.
Primary high tension wire from coil to distributor cap failing.
Distributor cap worn, or cracked.
Electric fuel pump not pumping (loose wire?)
Clogged fuel filter.
Clogged water/fuel separator.
Clogged carburator idle jets or main jets.

I've had several old cars (old Volkswagens and such) and when the ignition points get badly pitted or the gap slips closed, the symptom is exactly as you describe. Running fine, then quits, then fails to start or barely starts and dies.

Check your ignition point gap and file the points smooth if necessary, or just replace them, and check your distributor cap.
 

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My money is on a fuel delivery problem. Possible it's either clogging or the switch mentioned. I will bet the compressions have been in their current state for years.
 

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I'll second fuel delivery. Easy to find out. Just spray some go juice in the carb and see if it kicks.
Warning: the A4 has an UPdraft carburetor and its next to impossible to 'spray' into the carb. The updraft carb has a 'suction port' in the entrance throat of the 'flame arrestor' to prevent 'explosions' if this carb 'dribbles' fuel out of the carb and into the 'flame arrestor'.
 

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......This is my first full season, and it has been a tough one!
Unfortunately, you will become very jaded about the quality and honesty of many, if not most, marine maintenance facilities. If you ever find a good one that you really trust, pay them whatever they want.
 

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Warning: the A4 has an UPdraft carburetor and its next to impossible to 'spray' into the carb. The updraft carb has a 'suction port' in the entrance throat of the 'flame arrestor' to prevent 'explosions' if this carb 'dribbles' fuel out of the carb and into the 'flame arrestor'.
I am pretty sure that spraying some starting fluid into the updraft carburetor will not create a significant hazard. I know that the infernal combustion engine can be a confusing item for many, but that is certainly not the case for all. If you would wish to dis assemble the intake system to apply some go juice, head on, but not necessary.
 
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