Chainsaw gas mix in outboard

[mn_bowhunter]

Just got off the phone with my dad and apparently he put a gallon of 50:1 mix chainsaw gas mixed with synthetic oil. I believe it was stihl oil. This was added to about a gallon of 50:1 from last season mixed with conventional marine oil and stabil added. He said that the motor seemed to idle higher. My brother went to use the boat today and it seemed locked up to him. Is it possible that the chainsaw oil could cause a problem? I'm thinking it may be in gear so it can't be pulled over due to a stop on the recoil. The only thing that has me worried is he's had this motor since 1988 and if he says it's idling high it probably is.

[spearchucker]

I can't see where the gas would make it idle high. High idle could be an air leak in the engine or intake.

[mn_bowhunter]

After thinking more I remember him saying that it ran great when he put it in the lake. He noticed it was low on gas and put the chainsaw mix in because he wanted to get out fishing. That's when the high idle was noticed. I'm at a loss and am out of town so I can't look at it. I just told him to drain the tank and re-fill with new. I hoping it was just a temporary thing, but was wondering if anyone had a similar experience or knew more about mixing synthetic and conventional oils.

[jtroop]

There is a difference between 2 cycle oil for air-cooled vs water-cooled engines. That pretty much exhausts my expertise in the matter, however

[no bait nate]

I'm not to knowledgeable about these things but i've ran all kinds of two cylce gas including stihl oil through my 80's Johnson and it's all burned fine. i've noticed some slight idle differences but usually it's about a gallon of different gas mixed in with about 3 gallons of different gas. i always throw some seafoam in there and it all burns through. newer motors might be different but idk?

[theoilman]

Yes, there is a lot of difference (especially the additives) between 2-cycle oil for air cooled engines and 2-cycle oil for water cooled engines. Mostly it will have to do with deposits left behind because of the different temperatures air-cooled and water-cooled run. Though 1 tank shouldn't cause any catastrophic failure due to running the wrong oil type.

Sounds like something else is going on like the intake air leak someone else already mentioned. An intake air leak will make it run very lean fuel-air ratio, run hot and can easily burn a piston. Several other possible problems, you need a qualified tech to look at it.