pistons / rings for 1962 75 horse johnson

[ssschoeni]

My 62 johnson is at 90 - 92 lbs on all 4 cylinders and from what I've been told this is about 25 to 30 lbs low. I would like to rebuild the powerhead but I am having a hard time finding pistons and rings for this engine. Any ideas? Also, how much can I shave off of the heads before I have a clearance issue? I like running the old outboards but also like the boat to move better than 25 mph. ( 72 15' starcraft capri trihull )

 

[DJ]

Re: pistons / rings for 1962 75 horse johnson

Do this to the engine first. You may not need a rebuild.<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016 <br /><br />That engine never was a speedster. Solid as a rock but lacking in performance.

 

[Gunner56]

Re: pistons / rings for 1962 75 horse johnson

I have 80' 115 E-Rude. Compression check on the right bank was 30 PSI on both cylinders. Is decarbing worth trying first? The boat sat for a pretty good while. Head gasket was in good condition.

 

[ssschoeni]

Re: pistons / rings for 1962 75 horse johnson

I tried decarbonizing the engine and the compression went up only 3 pounds.( I have about 95 lbs per cylinder ) I'm guessing that it may just be the wear in the cylinders from the age. Any ideas where I can get a set of rings / pistons for the 62 johnson 75? Can I try just honing the cylinder bore and replacing rings?

 

[ledgefinder]

Re: pistons / rings for 1962 75 horse johnson

If all four are within 90-92, my guess is your cylinders are fine. It's virtually impossible to wear four cylinders that evenly. The low reading could be your gauge, slow starter motor, dirty solenoid, etc.. <br /><br />So why is the boat slow? Tough to say without more data, so these are guesses. Check WOT timing. Are the carbs (or is it that funky 4x1 carb?) clean? What prop pitch are you running - the motor may be lugging?

 

[ssschoeni]

Re: pistons / rings for 1962 75 horse johnson

The engine seems to run smoothly. It just has a hard time getting out of it's own way out of the hole and is at 25 mph on the top end. The carb has 2 throats and I did run the seafoam through both of them. It doesn't seem like it's hesistating so much as a lack of power. I'm running a 10 x 9 1/4 prop which seems to be the least aggressive prop I can find for that engine. The boat is a 15 foot starcraft capri trihull rated for a max of 85hp. When I checked compression I warmed the engine, and removed all of the plugs. The starter motor seems to turn fine and has plenty of torque and rpm to crank the engine. I was told by a tech here that the compression was just low and that is the reason for the power loss. I'm guessing it's probably the rings that have worn as I changed a set in a 1958 johnson 18 horse and it made a huge difference. For whatever reason it just seems to be hard to find the internals for the v4 engines in the 60's. Everything seems to start at 1975.

 

[Droll]

Re: pistons / rings for 1962 75 horse johnson

I think you engine uses many of the same part as my old v4 so :<br /><br />Rings / pistons : I got mine from this place Stone and Sons Marine (I bought ( last year)> .020 rings $58.33 )<br />Wrist pin bearings + rod bearings : Any Johnson dealer ?.<br />Head gaskets ( Sierra (Napa))18-2959 .<br /><br />But the first thing to do > remove the bypass covers and maybe the heads , then you can inspect the rings/cylinders/pistons .<br />Parts are available ,IF you know where to look .