Low Compression

[dobler5]

Hey I just did a compression test on an engine that has been sitting for awhile. All the cylinders checked out good for compression except for one cylinder. My question is: What will having compression low in one cylinder do to our engine? Will the engine not run properly? Could the compression comeback? Thanks

 

[wire2]

Re: Low Compression

What were the numbers? It could be as simple as 1 valve stem rusted slightly in the open position, and now not closing completely. It may fix itself with a bit of running.
Can squirt some oil into the low cylinder, if that raises the compression, it's bad rings. If not, might be a valve, possibly head gasket.
How bad 1 low cylinder makes the engine run depends on the number of cylinders; it's 25% of a 4 banger, 12?% of a V8.

 

[ENSIGN]

Re: Low Compression

What make and model of engine do you have and what were the compression readings???

 

[Unleadedaddict]

Re: Low Compression

Did you run the boat at all before the check? Generally if the engine has sat for a small length of time the rings have a tendency to stick or stay collapsed. Fire it up, let it cool and then check it.

 

[Bondo]

Re: Low Compression

Hey I just did a compression test on an engine that has been sitting for awhile. All the cylinders checked out good for compression except for one cylinder. My question is: What will having compression low in one cylinder do to our engine? Will the engine not run properly? Could the compression comeback? Thanks

Ayuh,... Waaay too little info to say....

 

[Don S]

Re: Low Compression

Hey I just did a compression test on an engine that has been sitting for awhile

.

Whatever the engine, hook up some water to it, start it and run for at least a minute and then redo the compression test.
Might want to read this service bulletin to make sure you do the compression test properly.

http://www.boatfix.com/merc/Bullet/97/97_25.pdf

 

[6meter]

Re: Low Compression

How bad 1 low cylinder makes the engine run depends on the number of cylinders; it's 25% of a 4 banger, 12?% of a V8.

One bad cyl in a V8 will make the motor run real crappy. You will lose 60-75% power. 4cyl even worse.