AV Gas (aviation gas)

[sweeper3]

Has anyone tried AV Gas in they're outboard. (100LL) 100 octane. leaded fuel???

I use it in everything that doesn't have a catalytic converter

Thanks very Much

Rob

[robert graham]

Most outboards are designed for and run fine on standard pump gas, 87 or 93 octane. Avgas is an expensive waste of money in an outboard motor.

[99yam40]

higher octane fuel burns slower and may not burn completely in the cylinder where it is designed to get all the power out, and may cause overheating in exhaust area if it is still burning in there.
Just my thoughts/opinion

[sweeper3]

I know the engines will work fine on pump gas, that's what i use. The question I was try to post was associated with the instability, phase separation, in pump gas (Mogas) or marine fuel vs AVGAS which has a much longer shelf life (up to 1year and many argue up to 5 years in a sealed can).

Right now AV gas is around 6.50/gal. I paid 5.35/gal marina fuel. It is more expensive, but if it lasts longer, doesn't have ethanol, increase's power and torque, requires little treatment. Why not???
The biggest problem I see is that I have to carry 12 5gallon cans to fill the boat.
It works great in my race car, and I've tested it vs the best racing fuels out there.(on a dyno) It equals and sometimes beats all the other fuels other than the most expensive VP race fuels. 40/gal

99 Yam- yes it burns slower, and yes there is an overlap in valve timing which could cause un-burnt fuel into the exhaust train. I have over 1500 hours with it in a 110 hp ford 4 cylinder. No burnt valves, or overheating.

Saying that, I don't know about marine engines. If anything the slower burn rate and the lead content effectively cools the combustion chamber.

Just trying to figure it out!!

Thanks for the comments and inputs

Rob

[99yam40]

4 stroke maybe but I would not run in a 2 stroke.
Hard or impossible to do any kind of adjusting timing on modern outboards with the electronic systems now a days that are set up for 87

[rodbolt17]

the lead was for valve face and seat lubrication,thats all it was for.
modern four stroke valve seat and face design doesnt use nor need the added lead deposits.
that high octane fuel works well with 2500 RPM aircraft engines at 16000 ft.
doesnt work well with full load 5-6000 RPM use that todays modern four stroke outboards need.
stick with the manufactures reccomendation and all is well.
in some EFI applications that use knock sensors or O2 sensors may suffer damage rapidly with leaded high octane fuels.