Cylinder Pressure (Help)

[raganjones]

Hello everyone,

I have a 1986 Mercury 175 outboard and it has been great. The boat mechanic today told the that the pressure in the cylinders on the left side are about 20 points lower than the right side.

He said it could last 3 months or another 5 years.

If they happen to go, I do not have the money to purchase a new engine, what is you recommendations?

Finding someone who can drop new power heads and rebuild???

I know this is a what if, but I want to be prepared for the next move if I possible can.

Thanks,

RJ

 

[CharlieB]

Re: Cylinder Pressure (Help)

Search these forums for 'Decarboning' there you will directions for mixing Sea Foam in a small tank to run the motor, and soak the piston rings and grooves to free any 'sticking' rings.

Afterwards repeat the compression test, if they improve, fine, if not, keep using a quality TCW-3 oil and forget about it till next year. Repat the compression test annually to see if it changes.

Curious, did he tell you the actual numbers? Can you tell us?

 

[jeffersondodson561]

Re: Cylinder Pressure (Help)

Was all of the cylinders the same compression on the side that was lower?

 

[raganjones]

Re: Cylinder Pressure (Help)

Charlie & Jeff,

Thanks for the replies.

the mechanic told me the compression was all the same of the right side...130 but the right side was 105....125....120.

With that being said, I went back to the year before tune up and noticed he had all of them at 120. May have meant 130, but not sure.

What do you guys recommend.

Thanks for the help.

RJones.

 

[jeffersondodson561]

Re: Cylinder Pressure (Help)

If those results are accurate, 20 lbs is a lot of variation to come back from, still I would do a decarb. I have read on here that sea foam works well, I have not used it but I know Yamaha's RingFree and Mercury's Quickleen and OMC's Engine Tuner I am convinced that works the best. After that I would recheck compression values myself. I would not be concerned with the actual pressure values but the variations of the cylinder. Anything more than 10lbs/10% could potentially be reason for concern.