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Antique Marine Engines and Outboard Motors

Johnson 3 hp fuel ratio

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Old 04-09-2019, 10:57:34 AM
Robrep Robrep is offline
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Default Johnson 3 hp fuel ratio

Hi i have a old Johnson 3 hp engine from around 1964. I got it going but think I put too much oil. (smokes real bad) I need to know what the ratio is with the newer 2cycle oils is. I remember back in the day we used to put a quart of 30 wt in the outboard can and fill it with gas. My dad called them stink pots because of the small. Thanks for any help you can offer.
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Old 04-09-2019, 01:10:20 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Johnson 3 hp fuel ratio

A quart of oil in a gallon can is about a 3 to 1 mix! WAY too much oil! First of all, you do not want to use modern lubes in that engine. It is too thin to lubricate the engine properly. You want to use SAE 30 non-detergent or 2 stroke OIL, not a synthetic or pre-mix lubricant. TCW type 3 2 stroke oil will work well too. You want to use a 16:1 fuel to oil ratio in your engine. 1 cup oil to 1 gallon of gas. Use marine gas if possible, or high test. Don't use E-10 regular auto fuel. If you used that quart of oil to a gallon can, I am surprised that that engine ran without fouling the spark plug! With the 16:1 ratio, the engine should smoke just a bit until it warms up. When warm, there should be very little smoke. If you are running the engine in a barrel or tub, exhaust gasses will be much more visible, as the exhaust is concentrated in the small water area. If running in a tub or barrel, you do not want to let the water get more than luke warm or you will damage the water pump impeller. Make sure your engine has water circulation or you will burn out the cylinders and water jacket near the exhaust ports.
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Old 04-18-2019, 11:09:12 AM
sylvan82 sylvan82 is offline
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Default Re: Johnson 3 hp fuel ratio

I have a 1963 / 3 hp twin cylinder that folds in half so it is able to fit into it's plastic carrying case. Out of the case the complete engine is 9" wide x 23" long and only weights 35 lb. Motor has a fuel tank and it's own fuel pump so I can draw fuel from my main fuel tanks. I keep it stowed under a seat in my 18' boat for a kicker motor. It beats the hell out of a wood paddle. I also use the motor on my 10' inflatable. For the last 40 years I have been using the same fuel mix as my 140 hp motor uses. (50 to 1)
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