I HAVE A 85 MERCURY 150 2 STROKE WHAT IS THE GAS /OIL MIXTURE?

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JT is right 50:1 is correct if it is not an oil injected engine or if the injection system has been disabled which is the case in my Mariner.
A friend of mine is a mechanic and with today's advances in oil technology he uses that mix in all 2 stroke engines that leave his shop.
Just make sure you use oil marked TCW (for two cycle, water cooled)
It is formulated to run at a bit diffrent temperatures then TC which is for two cycle air cooled....Show more

When you buy the 2 stroke oil that you mix with it. It should say on the back the mixture ratings... But usually its aroun 25-gas to 1-oil.. It can sometimes be 20 and sometimes be 30. But with a 150 most likely arounr 25-ish...

Those motors are bulletproof if you maintain them properly so you shouldnt have any problems with it unless you dont take care of it... Good motor though, even though it kinda looks ugly compared to the newer ones, just know it'll last maintanace free for much longer if you jsu have normal upkeep on it and stuff....Show more

All 1985 outboards run at 50:1. One pint oil per 6 gallons of gas, or 1/3 cup per gallon. That motor originally had an oil reservoir and oil metering pump -- guess a prior owner disabled that feature? Use any TCW-3 certified oil....Show more

hmmmm...check and see if you have an oil injection tank connected to the motor
if so, you could be causing a major problem if you mix oil with the gas - oil in the gasoline in an oil injected motor will cause a lean condition, and detonation
I have a 150XR2 V6 and it came with oil injection

edit:
Kudos to the usual top contributors JT, et al...
another minor note - if you are going to use E85 or any fuel with alcohol mixed in, you really need to use up all your premix in one season. DON'T use the old gas from last year - burn it in your car if you have to but drain it all out before next season....Show more

usually 25:1 or 30:1...Show more