35 hp Johnson Piston and ring replacement.

[restornator]

i'm working on a 77 35 hp johnson, it had <20psi compression on both cylinders after i installed a new powerhead gasket kit and head gasket. The cylinders walls are in excellent shape, as well as the pistons. I added some oil to both cylinders and got 140psi on the top, and still <30 on the bottom. with the spark plugs in, cranking it with a power drill, i can tell there is a lot of compression but my numbers are now <20 on both cylinders after it has sat for a good 6 months. I found a leak on the lower crankshaft seal, it was moaning when cranking it, and the moan was coming from a small leak. the crankshaft has a little surface rust but the bearings are all good. there's lots of varnish built up in the crankcase housing. I removed the pistons and the rings were not stuck nor scored. the fatter rings didn't have much spring in them. so my question is, should i replace the rings? And why are there .030 OS pistons and rings available?

 

[wilde1j]

Re: 35 hp Johnson Piston and ring replacement.

So when you get an out of spec block bored, the rings/pistons will fit properly.