1960's johnson fuel mix

So I just got a great deal on my first boat- a 64 14ft starcraft with 1960 18 hp johnson seahorse, trailer and trolling motor for $500.

I drained the gas and was unsure of the fuel oil ratio. Several websites and other owners say 24:1.
Some guys say that the oil today is much better than the oil in 1960's and that I should run it at 40:1 or 50:1.
And then I read that somewhere in the 1960's, the recommended fuel oil mix went to 50:1.

Why did the fuel oil mix change for motors in the 60's? Was there some sort of technology change?
All I'm looking for is to get the right mix so this motor runs well and I don't break something.

ski

i always run 32:1 and never fouled a plug or had a problem

fuel and oil were made different back in the day, they didnt have the additives and chemicles of today

40:1 should be fine in that motor, as the 18s and up were mostly jeweled motors. 32:1 won't hurt anything, if you feel it would be better.

General rule is 1960 - 1964 - under 18 horse - 24:1. 18 hp and up - 40:1

Post 1964 - 50:1, but on the smaller motors (3 - 6 hp) up until the mid 1970s, I'd run at 40:1, as they still have sleeve bearings.

The service manual for the motor states using a fuel to oil ratio of 24:1!! With today's better TCW-3 oil you could probably go leaner, but it would be safer to protect the bearings and stick with 24:1 fuel oil ratio. If it smokes a little too much for your liking use the synthetic TCW-3 oils and they are stated to be biodegradable and smokes much less. (Naturally they cost a little more).

* I reviewed this with a certified mechanic that has worked on these 40 plus years and he firmly states 24:1 fuel/oil ratio.

Mix for 24:1 is 16oz of TCW-3 oil to 3 galllons of gas

Mix for 24:1 is 32oz of TCW-3 oil to 6 galllons of gas

Good luck to you!! You got a good motor, so take care of her and she will take care of you!

cajuncook1

Thanks guys, especially cajun. I'll stick with 24:1.

ski

To answer your question...Yes, technology changed. The overall change from Bushings to bearings along the crank and rods allowed the leaner fuel/oil mix. Engines that have bushings should always be run on the richer 24:1 mixture regardless of todays oils vs yesterdays oils. Bushings simply require more oil to remain safely lubricated. The nice thing about todays oils in older engines is that they seem to smoke less. Yours should do well on 24:1 as it has a thermostat which will warm the engine and further reduce smoke.

Thanks for the help guys! I'm going to stick with 24:1 for now. It can't hurt, only help.

SKi

I've got the same motor! It's been great minus a little routine maintenance. Remember those old 2 strokes can gum up quick so always and I mean always run your gas out of the motor everytime your done fishing. If you look at my thread you'll see my motor. I repainted it, not to original but looks really cool. Those things will run like a scalded dog. With full tackle and gear plus me 190lbs I'll get anywhere from 19-23 mph on gps.
As for the oil/gas mixture- every outboard shop I've talked to in Little Rock, AR suggests 50:1. I've called around to verify this. Works fine for me.
Post some pics of your motor, I'd love to see how it looks.

Adam