One low compression cylinder

[wcmaness]

I have one - out of six - cylinders with low compression. The other 5 are at 100, with the 6th at 30. The piston wall shows some scarring, and the piston is not burned or busted, so I'm assuming it's the rings & scarring causing the low compression. My question is this: what problems will I have if I do nothing? I't idles a little rough, but otherwise seems to operate fine. I'ts been this way for a while - in fact it's run like this since I bought it 10 years ago. I know the fix is a rebuild (just that one, or do I have to do all 6 if I go this route), but I don't want to spend that kind of money on a motor this old. Am I ok just running like it is?

1985 Black Max XR2 150 V-6

 

[vegasphotoman]

Re: One low compression cylinder

Hi
running any motor that runs poorly...especially full throttle, can't be "good" for the motor....sounds like a repair is definetly in order,
I am no outboard mechanic...bit know a bit about motors.

have a mechanical buddy or neighbor take a look at the cylinder if you have the head off....maybye they see something / know something you dont

========2 strokes============
reeds can cause low compression on 2 strokes, does the motor spit back through the carb at all??

an old test is hold a business card 2 inches in frt of the carb, while the engine is running on water ears or in water....if the biz card gets soaked/wet with fuel = Bad Reed on that cylinder some fuel spit is ok...alot is not ok

if it is spitting back alot.....Reed repair shouldn't be too hard or expensive and would be worth doing in my opinion maybye $75 in parts total

===================4 stroke========
and a poorly seating valve on 4 strokes can cause low compression too, as can badly scored cylinder walls etc

if you have the head off, pour some fuel on the cylinder head depression where the valves are...while it is upside down...if the fuel runs out quickly into the valve intake exhuast runners...and the other valves depressions hold fuel....you may have valves not seating or burnt...pull valves on bad cylinder and check em out

hope any of this helps

 

[Dukedog]

Re: One low compression cylinder

Fix it now while it can be saved. Keep running it like it is and there may not be enough left ta save......................

 

[trendsetter240]

Re: One low compression cylinder

Fix it now while it can be saved. Keep running it like it is and there may not be enough left ta save......................

Agreed! Right now you may be able to get away with just rebuilding that one cylinder/piston assembly. If you leave it you may damage the crank.

Have a look at what I just went through.

http://forums.iboats.com/showthread.php?t=361179

 

[arcrat]

Re: One low compression cylinder

Try to decarb..
good luck.
arcrat