Fuel/Oil Mixture Difference

[Warpath42]

Hey guys. Quick clarification. I bought a 1965 Johnson 18 HP and used a ratio of 50:1. I had checked a forum and found that mix for that year. I had a problem with the motor and ended up buying a 1961 Johnson 18 HP. I did a quick clean up and then took it out on the water. Ran with no problems. The next weekend I took it out and as I was headed out from the ramp under full throttle power cut back. I ran it for a few more minutes then shut it off to fish. When it started it still didn't have full power. As I pulled up to fish it quit on me and I haven't been able to get it started since. I checked the FAQ and it says 1961 should be 24:1. I just wanted to check this was correct. Why such a big difference in ratio? I've also read you can play with the ratios. Would using the mix for the 65' cause the problem I'm describing or should I be looking for something else. One more thing this might sound stupid but I have a hard time with numbers, ratios sometimes. Like 12 gauge wire being heavier duty than 16 gauge, stuff that goes against the order. That said 50:1 is leaner, 24:1 is richer, there is more fuel, less oil in the 50:1. Am I getting that right. Which do I add to change 50 to 24, oil or gas. I'm thinking oil. Thanks for any help you can give.

 

[F_R]

Re: Fuel/Oil Mixture Difference

Your questions illustrate exactly why I am hesitant to reccommend using less oil in motors that actually can be run on less. Here you have a motor that won't run and right away you are blaming the oil mix when in reality there is no difference in the construction between the '61 and '65.

Anyway, the oil mix is not your problem, assuming you have at least 50:1.

To answer your other question, 50:1 is 1 pint of oil per 6 gallons. 24:1 is two pints of oil per 6 gallons, or twice as much oil. To change 50:1 to 24:1 you have to figure out how many gallons of gas you have in the tank and then add sufficient oil to bring it up to the ratio you are looking for. In other words assuming you have 6 gallons, you would add a pint of oil to the pint that is already in there. If you only have 3 gallons, you would add 1/2 pint to the 1/2 pint that is remaining in the tank.

OK, having said all that, that is not the reason your motor quit. An educated guess is that you have bad coils in the magneto. Check your spark. It should jump a 1/4" gap in open air.

I am assuming you didn't overheat it and burn it up because of a failed water pump. No burnt paint on the powerhead, I hope.