1958 35hp seahorse compression

[ohmydog]

model RDEL. Ran alright, but a little rough and a bit sluggish on the water. Came home and checked a few things out. Did a compression test at running temp and got readings of 95 on the top and 75 on the bottom. Not what I was hoping to see. Any suggestions for what to do next for a notverymechanic-ybutwillingtotry guy?

 

[racerone]

Remove the 2 bypass covers on the side of the block.----That allows for inspection of pistons and rings.

 

[boobie]

Could also be a blown head gasket.

 

[F_R]

How are you doing the compression test? If you are using the electric starter, those numbers are way too low. If you are using the recoil starter, have you disabled the compression relief valves? If not disabled, you will get a false (low) reading. That's what they do---relieve the compression somewhat for easy pulling.

EDIT: Also make sure the compression relief valves aren't being held open all the time. There should be clearance between the rocker arms adjusters and the valve stems when the rope is retracted. A partially pulled starter rope will hold them open. So can a rope that is the wrong length.

 

[ohmydog]

The tests were done using the electric starter. Compression release valves were not engaged.

I am calling out a favor from a neighbor of mine that has a bunch of experience with Johnson/Evinrude motors. He'll drop by in the next couple days and I'll report back on what we see. Admittedly, I'm in a bit over my head and need some outside help to learn how to deal with this....or not.

 

[1946Zephyr]

That does either sound like a head gasket or possibly a ring issue. If the motor was ever overheated, that could score the pistons up and make the rings stick in their grooves. Like FR says, theck the compression release arms on the head and see that there is a small gap between the adjusting screws and the little valves
If you do pull the head, inspect the cylinders for any damage as well