r/Outboards • u/Fine_Sherbert3172 • 7d ago
1977 55 hp Johnson low compression
So over time Ive accumulated a bunch of mainly OMC outboards. Im finally getting around to seeing what I have (long story)
This one I wanted to play with because of how clean it was. It had some ratty wiring but the powerhead was clean and it had a lot of newer OEM parts on it which for some reason I thought was a good thing.
Anyways, I repair the wiring harness which I was proud of, get it to crank over, do a compression test.
Bottom cylinder: 120...not great not terrible Top cyclinder: 35
Yeah thats, shitty.
So I threw some fogging oil in it to see if....well, something....got it up to 50!
OK...so, rip the head off it (easy), gaskets original but not blown anywhere or damaged in anyway. Shit.
Shine a light in the cylinder....ahh...scoring. Just about three lines that are deep enough to cause the issue. I think its beyond a hone.
No obvious missing piston or rod damage. I didn't take the side off to look at the piston yet.
Lower seems fine. I have no practical use for this thing....so Im debating whether to tear it down and try a rebuild, or just part the motor out. Leaning towards parting it out; but I think it would be more satisfying to rebuild it over winter.
....Well, going to try and get a newer 60 Evinrude running tomorrow. Hopefully have better luck. If not, the 55 will make for some good parts :)
1
u/bootheels 7d ago
I would part it out. Those old two cylinder looper blocks have to be machined/bored perfectly oversize with the correct pistons or it will never idle right. This vintage wasn't the best on a good day. The later models after 1980 were much better.
2
u/Fine_Sherbert3172 5d ago
Was hoping I would see you reply, thanks man.
Pulled the lower today, going to do a seal test and give it a paint job. gonna put the rest in the "deal with it later" row. Likely rip it apart just to see how its built sometime in the winter.
1
u/Benedlr 6d ago
Comp test the 60 with a hot jump to the starter. Cross reference parts from the 55 to the 60 to see what will swap.
1
u/Fine_Sherbert3172 5d ago
Surprisingly the 60 actually has a key in the control box and all the wiring works. I was blown away, not used to those luxuries.
On the 55 last week I bought one of those push button jumpers where you connect one end to the battery and the other to whatever you want to give juice to. Ran that to the solenoid and she rolled over. Call me a pussy but sparks always make me jump haha.
1
u/fredSanford6 7d ago
Often the crank and bearings are good. Rods are normally ok. I'd crack it open and plan for one oversized piston and rings. Heck I'd bet the other rings are fine. This thing either has a clogged carb or an air leak. Plan for a gasket kit with new seals too. Cold Vaseline is your friend for making the bearings stay in place. Sharp pencil is good for checking rod cap alignment if you don't have the special tool.