Re: 10 HP Johnson
24:1 is the correct mix. they didn't go to 50:1 until around 64-65. you may even want to run a gallon of 16:1 through it for starters just to get the innards well coated with fresh oil after sitting for so long. always better to have a bit more oil than not enough. 24:1 is roughly 5.5 oz per gallon, but I just round up to 6 oz. per gallon. It may smoke a bit in the test tank and the water will get pretty oily, but once you're on the open water it won't smoke much at all. I get very little smoke out of my '61 running 24:1 on the open water, especially after you decarb it and get the funk out. You can get sea foam at any auto parts store for about $10 a can. It's white and has sort of an old fashioned logo and lots of writing on it. Just ask for it and they'll show you where it is. It's great for your car, truck, lawn mower, or practically any other internal combustion engine. Best $10 you can spend on a motor IMHO. You can get it in liquid or spray form, either one is fine. The spray version is kind of nice because you can spray the sea foam directly into the carb throat as the motor is running as another way to decarb it. Do a youtube search, and you'll find all kinds of vids of folks sea foaming their cars, trucks, boats, etc....They might be worth watching just so you know how much smoke to expect. Good luck. Keep us posted.