Measuring oil for the outboard

About half the outboard motors you see in the Bahamas or Caribbean are 15 HP two stroke Yamahas. This is a popular choice because it weighs less than a 4 stroke 9.9 HP, and you have the horsepower to plane a RIB with 4 adults. This tip won’t help you if you have a 4 stroke engine, but if you have a 2 stroke leaf blower at home; this can work for you there.

I find this device to be a real convenience. It is for measuring the correct amount of oil to mix with the gas. It beats trying to figure the right amount of oil to mix with say 3 ½ gallons of gas at 50:1 ratio. I also find it difficult to read the ounces on the side of the quart containers of outboard motor oil when trying to measure out the oil.

The way it works is that you choose the ratio column you need, say, 50:1, and fill the bottle with oil up to that line. So as you see in the picture, there is a line at the 6 gallon mark. Don’t be confused by the number on the left. This is the equivalent in liters of the gallons of gas. Fill the bottle up to this line, and you have the correct amount of oil.

If you were to do the calculations for 6 gallons of gas at 50:1, you would come up with 15.36 ounces of oil. I think, is that right? Yes it is, but I needed a calculated to do this, and still double check it. Filling up to the line is a lot easier for me.

Follow your manufacturer’s recommendation for the oil to gas mixture. You may see anything from 25:1 to 100:1. I’ve owned a Yamaha Enduro outboard with a recommended mixture of 25:1, and my current 15 hp Yamaha owner’s manual recommends 100:1. But, after talking to several experts, they all suggested that I use a 50:1 ratio, not 100:1. They said that my motor was sold in the USA, and at the time, our EPA had a regulation not allowing a richer oil mixture than 100:1. These experts said that my engine would last much longer if I used a 50:1 mix, and that it would not hurt the engine. I’ve been doing this for years without any problems, and so have other cruisers I know