Low compression in one cylinder

[Alex81]

I have a 1993 200 Hp Mercury. Five cylinders are reading 130(compression) and one is giving me 105. The engine sounds and runs good on the water. I was told that i have to repair the motor. I will like to know if there is anything else that could be causing this issue (I hope i don't have to).

 

[emckelvy]

Re: Low compression in one cylinder

Decarbonize the motor as per the below link, if the compression in the low cyl doesn't come up, pull the cyl head on that side for an inspection. If the cylinder is scored, you're looking at a rebuild. Be sure to investigate the cause and correct as necessary to avoid another failure (such as lean running, etc).

http://forums.iboats.com/showthread.php?t=158076&highlight=seafoam

HTH..........ed

 

[Alex81]

Re: Low compression in one cylinder

Thanks for your help. I hope that this will solve the issue. Thanks

 

[sschefer]

Re: Low compression in one cylinder

Is it 1 or 5 that's low?

 

[Alex81]

Re: Low compression in one cylinder

Only 1 cylinder. All other 5 have great compression.

 

[sschefer]

Re: Low compression in one cylinder

Only 1 cylinder. All other 5 have great compression.

Sorry, should have been more clear.. What is the number of the cylinder that's low. Is it cylinder #1,2,3,4,5 or 6?

 

[Faztbullet]

Re: Low compression in one cylinder

Low compression can be caused by several things on a 2.5 liter:
A) Rings stuck due to carbon ( doubt thats your problem as others are fine)
B) Bad head gasket
C) Damaged cylinder/piston from electrical or mechanical failure
D) Reed block or reed problem on that cylinder

 

[Alex81]

Re: Low compression in one cylinder

How much a repair like this could cost me? Any suggestions.

 

[Fuzzytbay]

Re: Low compression in one cylinder

The repair cost, is directly related to the problem. So unless you know what is wrong, its not really possible to say how much it will cost to fix it.

 

[robert graham]

Re: Low compression in one cylinder

If the motor is running well, then do the heavy de-carb procedure with Seafoam and hopefully free up stuck rings/carbon deposits, re-check compression. If it gets better, then de-carb again. You could remove exhaust cover to inspect pistons, rings, cylinders, etc. You may not have a great big problem. Good luck!