No compression at all????????

[woollums]

I have a 2004 Mercury 50 3cyl 2 stroke outboard that has zero compression on all three cylinders. Any ideas? Do theses engines have reeds?

 

[JB]

Re: No compression at all????????

Whether it has reeds (which it does) is immaterial, woollums. They seal the crankcase, not the cylinders.

What is the history of this outboard? Sounds like a case of severe abuse/overheat/carbon/head gasket or warpage.

You need to do a physical inspection.

 

[roscoe]

Re: No compression at all????????

WWWWHat JB said.

Motor new to you?

History?

Something is not right.

 

[woollums]

Re: No compression at all????????

Its new to me

 

[CVX20SPRINT]

Re: No compression at all????????

Not just a screwed gauge is it?

 

[Silvertip]

Re: No compression at all????????

No head gasket on those engines. Are we to understand you bought this engine that way? If so, what the seller told you may allow some legal recourse. If he advertized the engine, what the ad said may also be ammunition for you. So give us something to work with. All we know is it has no compression. Who checked it. You can remove the spark plugs and look into the hole with a pen light while having someone turn the flywheel. You may see a hole in the top of each piston. What do the plugs look like? Was the engine running ok for you and then something happened? You did know about keeping the oil resevoir full did you not? Sorry that we have more questions than answers, but we can't see you engine and you haven't given us any details.

 

[woollums]

Re: No compression at all????????

Ok, sorry for the lack of info. I'm a pretty decent atv and pwc mechanic, but i've never even seen inside a outboard engine before.

I just purchaced a neglected 20' pontoon and this engine was on it. The guy i purchaced it from said it stoped running the summer before last. The boat was setting in the gulf docked for along time and has a unreal amount of barnical build-up on the pontoons. The engine looks real nice though. I replaced the fuel, fuel line, plugs, and cleaned the carbs. I looked in the cylinders with a pin light and the top of the pistons looks nice, but i cant see the walls of the jugs. I put my finger over each plug hole and there is very little pressure when cranking. It also spins pretty easy by hand with the flywheel. The old plugs didnt give much to go on either. Its possible that barnicals blocked the cooling ports and it was over heated. I dont mind rebuilding it if need be. What other than piston/rings on these engines could cause 0 compression? Do they have decompression setups or could the it be crank seals?

 

[Silvertip]

Re: No compression at all????????

Crank seals wouldn't cause total loss of compression. A severely overheated engine causes the rings to lose their tension. The overheat may also have caused severe cylinder scoring. the only way you will know is to tear it down. Be aware that this engine does not have a removable cylinder head. Therefore rebuilding is a little different than a standard block with a removable head. If you pull it apart and fiind serious damage, you might want to look for a used power head or a rebuilt power head. The water pump is in the lower unit and it would need to be replaced as well.