Compression

[Tbass121]

I have a 1983 115hp envinrude, my compression is 60-85-85-85, is this an acceptable results?

 

[dstroud1987]

Re: Compression

I have a 1983 115hp envinrude, my compression is 60-85-85-85, is this an acceptable results?

well im definitely no expert here.. but I've recently been asking a lot of engine questions.. and from what everyone tells me, the most important thing about the compression is that all cylinders are within 10% of eachother. I think the one with 60 is probably ging to prove to be a problem for you.. how does the motor run? are you having problems with it?

im sure someone with a lot more knowledge than me will post up some good stuff to help you out soon anyways.. good luck with it!

 

[86 century]

Re: Compression

The numbers are low across the board. The 65psi is the big problem that cly is gana need some work.

I have tested a bunch of older johnnyrudes I would say that one is near the end of its life with the one hole down to 65 probably having a melted piston.

 

[Gus-71]

Re: Compression

Hi!

The cheapest thing you can do is to pull off the head of the side that has the 65 psi and see for damage.
You could be lucky... perhaps a bad head gasket, but with 85 psi on the others I?m worried.
Sorry to say It seems like the motor is a little worn
Anyway good luck!

Gus

 

[JB]

Re: Compression

Howdy, Tbass.

Welcome to iboats.

So three cylinders went bad by the same amount at the same time?? Not likely. Much more likely that the 85psi are the result of imperfect gauge or technique on sound cylinders.

The 60 psi cylinder needs attention but it is not dead.

First, do a decarb. #1 probably has carbon stuck rings and a good decarb will clear it up. No way would a melted piston compress 60psi.

Far too often people go in for expensive major surgery when a good dose of preventive maintenance would solve the problem. Always try the simple, inexpensive stuff first.

 

[emdsapmgr]

Re: Compression

Those engines were some of the first to use the low compression bathtub heads. 95 lbs compression is probably normal, but 85 is not that low on a high-hour powerhead. As everyone has noted the 60 lb cyl. is the problem. Pull the head off and see if the seal ring on the head gasket is damaged-might be an easy fix. If the head gasket is the problem, agree with JB on the decarb.

 

[boobie]

Re: Compression

Were all the plugs out when you did the compression test ??