[CT-Kurt]

I bought a used 70 HP Yamaha 2 cycle oil injected outboard. It doesn't seem to be using much oil from the oil injection tank mounted under the engine cover.I've used about (4-5) six gallon tanks of gas and the level in the oil tank dropped to only about 75% full. After little oil useage with the first six gallon gas tank, I started adding a 50:1 mix to the gas tanks.Anyone have an idea of how much oil the engine mounted oil tank holds and what I should expect for oil usage?Thanks

[lonewolf5347]

CT-Kurt on my yamaha 90 hp 2003 the oil tank will hold a gallon of two cycle oil tank mounted under the engine cover.yes I would premix your gas and oil the amount of oil does not sound right.What you can try is to fill the onboard tank with oil premix 6 gal of gas (you will run rich)run the six gallon of gas out you should be able to refill the tank with 16 oz of two cycle oil.

[jim dozier]

Buy a manual and read how to do the oil injection service. Common problems that may be simple are kinked oil lines, clogged (old 2-stroke oil can gel) tank pickup, and clogged oil filter/screens. The manual will tell you how to test the pump output. Mix the oil 50:1 until you know the results.

[Capt Ken]

Those tanks hold quite a bit of oil. If you figure four six gallon tanks of fuel, then to have a 50:1 ratio, you would have needed to use four pints or two quarts out of the tank. Not much when you figure that tank probably holds close to a couple of gallons. Plus, you probably didn't use all the fuel in the fuel tanks before you refilled which would have reduced the amount of oil used. The 50:1 ratio is fine for high speed running but too rich for idling. That's why the control rod on the pump is connected to the lower carb. It varies the ratio depending on the speed of the engine. At idle, the ratio is closer to 100:1.