73' 85HP JOHNSON LOW COMPRESSION

[rbbrox]

My question is, will it hurt the motor if the #4 cyl is running compression of 75 while the other 3 cylinders are running 105 to 110. Seems to be running ok just a little rough at low RPM. Though stays running no problem. Not ready to put big bucks into this old fella.
Thanks

 

[iwombat]

Re: 73' 85HP JOHNSON LOW COMPRESSION

It's probably indicative of a problem - something like stuck rings or a leaky head gasket.

 

[ezeke]

Re: 73' 85HP JOHNSON LOW COMPRESSION

Don't put big bucks out, just buy a cylinder head gasket, take off the head and see whats up. If everything looks OK, do a decarb and see if things improve.

Running like it is is too risky.

How did the spark plugs look when you took them out?

 

[F_R]

Re: 73' 85HP JOHNSON LOW COMPRESSION

Yes, you do need to investigate. It could get a LOT worse VERY fast. I'd say don't run it at all till you see what is wrong and correct the problem if it's correctable.