1997 Johnson 25hp to 35hp 2 stroke 3 cyl. conversion - prop decision

[captbone]

I would get a good 15pitch SST OMC wheel. Have it labbed and it should run pretty good. I would also raise the engine up on the transom 1/2-3/4 inch.

25:1 oil ratio seems crazy to me. Not even insane race engines run that. 50:1 should be fine in my opinion.

[speedfreak]

Going try a 14P OMC first see where that puts me and go from there. I already have it raised off the transom 1 1/2" and have went back to 50:1 ratio. I saw no difference (performance wise) from 25:1 to 50:1, other than it didn't smoke as bad.

[JohnsonM50]

Going try a 14P OMC first see where that puts me and go from there. I already have it raised off the transom 1 1/2" and have went back to 50:1 ratio. I saw no difference (performance wise) from 25:1 to 50:1, other than it didn't smoke as bad.

Oil, If you have to endure 'go-slow' zones like around here excess oil could foul up the works I guess but if your mostly WOT then probably not, Whats right? [the 64 Dollar question]. If your within the stock motors rated RPM's then 'book' mix is fine. When you run 1000-1500 R's above, then more for sure. 32:1 seems to be a happy medium or even more on a hi value vintage motor.

[Mark Poole]

Keep in mine that all OMC portable motors (35 and under) were made to run on crap fuel. They told us at school one year that small OMC's can run down to 70 octane. Lot of room for carb and timing mods knowing that. Also, no need to run extra oil in one of these little motors especially if you are not turning it carzy rpm's. Use a thinner, 75W 90 synthetic gearoil instead of 80w90 for longer gearlife and a few more rpm's.

[speedfreak]

Thanks Mark, Good info! What is your definition of "crazy RPM's". I am currently hitting my rev. limiter at 6200R's, hence why I'm going up to a 14 pitch from a 13 pitch. Also, I am sending yo a PM!