Atomic 4 compression - Page 3 - SailNet Community
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post #21 of 24 Old 09-21-2011 Thread Starter
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Thanks for all the feedback. My bet is fuel delivery as well, but the Marina refuses to call me back after diagnosing low compression.

I can't even get an estimate to tell me how much to properly diagnose.

To answer someone's earlier question, I am in Manhasset Bay in the Western Long Island Sound.

Looking for another mechanic.
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post #22 of 24 Old 09-21-2011
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From the sounds of it, I don't think I'd be wanting a call back from that particular shop, let alone waiting for one.

The "she sits sometimes for a month or more at a time" comment is very telling. The A4 begs to be used and is most well behaved when she is. Today's Ethanol laced fuel is creating havoc in older engines, marine or otherwise, because they weren't built with seals and gaskets that were expected to be exposed to that. Couple that with the tough life they lead living in Saltwater most often, and you've got "issues" when left alone. Down here (Florida), I find it best to at least clean my carbs once every year and rebuild them at least every other year. When was the last time that was done on this particular unit? The fuel system hints have been good ones and you should follow those recommendations posted. I for one, would've assumed the entire fuel system was bad when they replaced the pump and had every inch of hose put in new. Good luck and I hope you get someone that can help get her back to chugging as nothing is more frustrating than spending all your time "fixing" and none "enjoying" the boat.
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post #23 of 24 Old 09-21-2011
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There is a quick and dirty compression test I learned from Moyer. Remove the spark plugs and press your thumb on the spark plug hole. Crank the starter. If you can hold your thumb there and no air leaks out compression is inadaquate. If air leaks out compression is ok. Low compression on adjacent cylinders is usually a bad head gasket. Is the crankcase oil milky? If so water is getting in the oil which is the head gasket, The exhaust manifold or a leak between the waterjacket and the crankcase.

If this happened after Irene the motion of the boat may have stirred up gunk in the gas tank causing proplems with the filter or carb. Definately get another mechanic
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post #24 of 24 Old 09-22-2011
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Quote:
Originally Posted by fordo View Post
There is a quick and dirty compression test I learned from Moyer. Remove the spark plugs and press your thumb on the spark plug hole. Crank the starter. If you can hold your thumb there and no air leaks out compression is inadaquate. If air leaks out compression is ok. Low compression on adjacent cylinders is usually a bad head gasket. Is the crankcase oil milky? If so water is getting in the oil which is the head gasket, The exhaust manifold or a leak between the waterjacket and the crankcase.

If this happened after Irene the motion of the boat may have stirred up gunk in the gas tank causing proplems with the filter or carb. Definately get another mechanic
Much ta doo about little. The reality of the situation is that the head could be yanked off in an hour and taken to the local machine shop for all of the head work for cheap. A gasket set and some very basic hand tools and it would take longer to clean the bolt on parts then to re assemble. All top end work would be fresh no questions.
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