1990 OMC Cobra 4.3L - 0 Compression

sikemd

Cadet
Joined
Jul 20, 2009
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I have one cylinder on my OMC that has 0 compression. I was having some problems earlier this week, loss of power and a ticking sound, as well as some abnormal vibration. I went to replace the plugs and wires today and found one of the plugs I removed was pretty much destroyed and the wire was a bit burned up. This is the cylinder that has no compression. There is no irregular noise coming from the engine and the ticking has stopped, presumably one of the wires was arcing out. A boat mechanic friend of mine says there is a possibility it is a valve or something that would not require the engine to be pulled and suggested pulling the cylinder head and getting a better idea of what happened before I go making any serious decisions. I am mechanically inclined but I am not interested in pulling the engine or paying to have it replaced. I'm going to attempt to remove the cylinder head sometime this week and get a peak into what is really going on but until then I wouldn't mind a little feedback on the situation.
 

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HT32BSX115

Supreme Mariner
Joined
Dec 8, 2005
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Re: 1990 OMC Cobra 4.3L - 0 Compression

I have one cylinder on my OMC that has 0 compression. I was having some problems earlier this week, loss of power and a ticking sound, as well as some abnormal vibration. I went to replace the plugs and wires today and found one of the plugs I removed was pretty much destroyed and the wire was a bit burned up. This is the cylinder that has no compression. There is no irregular noise coming from the engine and the ticking has stopped, presumably one of the wires was arcing out. A boat mechanic friend of mine says there is a possibility it is a valve or something that would not require the engine to be pulled and suggested pulling the cylinder head and getting a better idea of what happened before I go making any serious decisions. I am mechanically inclined but I am not interested in pulling the engine or paying to have it replaced. I'm going to attempt to remove the cylinder head sometime this week and get a peak into what is really going on but until then I wouldn't mind a little feedback on the situation.


Howdy,


Yeah, ZERO compression (all of a sudden) is usually from a detonation "event".

Pull BOTH risers, manifolds, and both heads so you can compare.

You WILL find the problem. It may only be a burnt valve that a machine shop may be able to "fix".


You won't know until the heads are off. AND I wouldn't just pull the one with the low cyl....



Good luck,



Rick
 
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