Fuel and 2 cycle oil mixture?

[Schnidly]

Dear Forum, Can someone tell me the correct mixture of fuel and oil for my 1984 2cycle Mercury 3.5hp outboard? Is it ok to use 2cycle Stihl oil, used for chainsaws and other 2 cycle engines? I am guessing the fuel to oil mixture is 50:1? Just not sure. This is an older 2 cycle outboard and I know that some people use the Stihl chainsaw 2 cycle oil, I just want input if this is really ok?

 

[batman99]

Recommend...

50:1 mixture - 1 pint of TCW-3 outboard oil to 6 gallons of gas. Or about 2.65 ounces of oil per gallon

Also... Try to use TCW-3 oil - which is rated for marine usage.

For me, I use a measuring bottle like: http://www.americanparagliding.com/quick2mix.htm
Note: Shop around - prices for this mixing bottle dramatically varies

Hope this helps.

 

[Alumarine]

I'm going to guess 50:1 as it usually is for this era of motor.
Reason I'm guessing is that it is very small and I'm not familiar with them.

Chainsaw oil is not suitable for water cooled boat motors.
If your motor is water cooled don't use it. Use a TC-W3 rated oil.

 

[emckelvy]

Well, this is an odd one, 'cause normally one would use TCW-3 oil in an outboard, but your 3.5hp appears to be air-cooled. Therefore it wouldn't take TCW-3.

I can't see where Stihl oil meant for an air-cooled 2-stroke chainsaw would hurt the engine; it's a quality oil.

I don't have the factory info on fuelil ratio on that one but air-cooled engines do run hotter than a water-cooled 2-stroke; a 32:1 mix isn't extremly oil-rich and would give extra protection to the internals.

Make sure that whatever oil you might use is rated for air-cooled engines, and, preferably, low-ash.

Be sure that if you ever run a water-cooled outboard, use TCW-3 at a 50:1 mix, you don't ever want to run a water-cooled outboard on air-cooled oil.

HTH............ed

 

[GA_Boater]

Recommend...

50:1 mixture - 1 pint of TCW-3 outboard oil to 6 gallons of gas. Or about 2.65 ounces of oil per gallon

Also... Try to use TCW-3 oil - which is rated for marine usage.

For me, I use a measuring bottle like: http://www.americanparagliding.com/quick2mix.htm
Note: Shop around - prices for this mixing bottle dramatically varies

Hope this helps.

I also recommend shopping around.

The two on the bottom are from iboats and you can get the Seasense bottle with shipping for less than the $10 bottle as well as help pay for the forum. http://www.iboats.com/Boat-Parts-Ac..._category.f--searched.1--session_id.562785960

 

[MTboatguy]

What is the serial number on that motor, some of the 3.5 hp 2 stroke motors are actually water cooled. If it is water cooled, it uses different oil than an air cooled model.