New here couple questions...

[T-Duh]

I'm new here and somewhat new to boats. I boat a 1980 skeeter bass boat last fall real cheap without hearing it run. It had a 90 horse Chrysler which I was sure before I bought it was gonna be junk, turned out the bottom piston was burnt up. This spring I picked up a 1973 65hp Johnson, came with controls and everything and i had a "boat mechanic" put it on for me. This guy was a real treat, he did a half arsh job and left me with plenty to still do. I've read quite a bit on here already and alot of questions have already been answered, thanks to a ton of great info. But I have a couple more. First thing is he told me he compression tested the motor, his results were a little better than 70 psi on all three cylinders. He told me this was normal because when he did it he was just turning the motor over by hand. Will compression tests vary from turning over by hand and cranking with ignition? I've got a few other questions but that's the main one. I dont wanna drop anymore money into it if it needs rebuilt. Thanks guys, btw I know the compression should be well over 100 all the way across the board. Thanks in advance!

 

[JB]

Re: New here couple questions...

Howdy,

Welcome to iboats.

If all three cylinders compress very close, regardless of the poor technique, your engine is probably healthy. If he is pulling the engine through by hand, I would call 70psi good.

A proper compression test, as described in the Top Secret File ^^ would certainly show higher numbers, but they would still be close, so the change would mean nothing.

You do not "know" that compression should measure over 100psi. You merely believe that, and it is not true. Compression should be even. If all conditions were ideal and the test was done correctly with a good guage 100psi might happen, it might not.

Three cylinders do not all go bad by the same amount at the same time. Rules of thumb learned on 4 stroke auto engines do not work on 2 stroke outboards.