Low compression on one cylinder

D

dtwalters

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My 89 200hp Evinrude is showing 70psi on one cylinder and 89-90 psi on the other 5. I had the head off last year and saw no bad scoring of cylinder walls. I replaced the head gaskets then and have not ran it since. Today after rebuilding the carbs I ran it and found the above compression readings. I am doing a decarb to see if it is a stuck ring or carbon build up. If the copmpresion does not improve what would you guys suggest? Is this old of an engine worth putting much money into? The engine probably has 500-600 hrs on it.
Thanks for your help.
David
 
D

dtwalters

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Re: Low compression on one cylinder

Also the engine starts and runs very good, although I have only ran it on ears since I've foung the low compression. any comments would be appreciated.
thanks,David
 
kenmyfam

kenmyfam

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Re: Low compression on one cylinder

dtwalters said:
Also the engine starts and runs very good, although I have only ran it on ears since I've foung the low compression. any comments would be appreciated.
thanks,David
Click to expand...

Let's see what the decarb does for you.
 
D

dtwalters

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Re: Low compression on one cylinder

After spraying seafoam into the bad cylinder last night and letting it soak, I checked compression againa fter warming the engine up, and found around 70 psi. I squirted some oilinto the cylinder and the compression checked it and found 90 psi.
What would be the next move? I'm thinking pull the head to inspect the cylinder and top ring. And also check the head for warpage. any other sugestions? Is 20psi difference too much to operate engine with?
David
 
D

dtwalters

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Re: Low compression on one cylinder

I spoke with the local outboard tech and he said he would not tear into the engine at this time. He suggested added extra oil and running it. I asked about the possibbilty of head warpage but he said they see very little of that. I did have the engine in an overheat situation once (shallow water) where the engine went into slow mode. What say you?
David
 
ondarvr

ondarvr

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Re: Low compression on one cylinder

You didn't do a decarb by just spraying some into the spark plug hole and letting it sit.

Do a complete decarb and it may come up. There are instructions in the FAQ section.
 
D

dtwalters

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Re: Low compression on one cylinder

Ondarv I mixed a can of seafoam with about 1 1/2 gals of gas and ran that through and also sparayed each carb with omc power tuner.
 
ondarvr

ondarvr

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Re: Low compression on one cylinder

All I can say then is try it again, some people report it may take as many as three treatments to bring it back up. I'm not saying it will work, just that for the money its at least worth a try.
 
D

dtwalters

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Re: Low compression on one cylinder

I think I will pull that head off and take a look at it and if I can't find something that stands out at me I will follow up with some more decarbing. Thanks for your help. I will let you know what I find.
David
 
8

83ebbtide

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Re: Low compression on one cylinder

If you opt for the decarb again try tilting the motor all the way up and spraying the seafoam into the plug hole and let it sit again overnight. With the motor up it allows the seafoam to soak on the rings better.
 
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