Water and scoring in center cylinder - '75 Evinrude 70hp

jhetrick55

Petty Officer 3rd Class
Joined
Apr 21, 2017
Messages
83
In the fall of 2016 I purchased my first boat - a 1988 Sierra, 16' Fiberglass fishing boat - and it came with a 1975 70HP Evinrude engine. I took it out once in the fall before I worked on the interior all winter in my garage. It started hard, but ran after I used the manual choke. The only issue I noted was a lot of smoke upon starting for the first time in I don't know how many years. I was pretty happy it ran at all.

Come spring of 2017, I take the boat out and start it up the first time, a lot of smoke, but again its running seemingly well as the engine warms up. I take the boat out again a few days later, smoke upon starting, but runs well. This happens several more times, along with having to use the manual choke to start the engine nearly every time, and I am starting to think there is a bigger problem.

Long story short, I take the boat in to a dependable mechanic and his assessment is that water is getting in the center cylinder and it must be a cracked block. I read up on this to find out it could also be a head or exhaust gasket. I take the boat elsewhere for a second opinion. The second opinion tells me they didn't even get to the place where they ran the engine to know if water is getting in, but they have found scoring on the center cylinder - to what extent I will find out tomorrow morning.

So, my question is: Will the engine run with scoring (compression tests have 125-130psi for compression in each cylinder) if I can find the source of water getting in? Tomorrow morning I am meeting with the latest mechanic to have him show me what he is seeing. After that I may be able to make a better determination about proceeding by buying a different engine or repairing this one.

In the meantime, any thoughts or experiences will help. Thanks!
 
Last edited:

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,300
Motor is 42 years old.--------could well be the exhaust cover gaskets.----Or the cylinder head gasket.
 

jhetrick55

Petty Officer 3rd Class
Joined
Apr 21, 2017
Messages
83
A brief update. The most recent mechanic said the opposite of water in the cylinder... he said there was some scoring from probable previous overheat, but no evidence water is getting in to that cylinder. He said I shouldn't be able to run it for more than 100 yards and it would shut off. I have run it far more than that and it has run fine. Right now I am thinking if anything I may up my oil ration a bit and just run it until it won't run anymore while I look for a new engine... either that or until the end of the year and then rebuild over the winter.

Thoughts?
 
Top