Avgas in my boat?

[SecondMonkey]

I have a boat with a restored 1972 Mercury 150hp engine. These engines are notoriously picky about the fuel they drink. Mercury even lowered compression in later models due to the newer urine-like fuels.

Anyway, I was thinking about trying some 100LL avgas in the motor this year, mixed with regular 87 to around 95 octane. Partially because of the ethanol in regular gas, and partially because regular gas is garbage.

Anyway, will this cause any harm in a carbureted motor? My dad used to run it in his '67 Ford, but claims the "antifreeze" in the gas ruined his carb and apparently eats rubber. On the other hand he's really clueless about gas/oil and I doubt he has any idea what ruined his 40 year old carb...

 

[Big Jim]

The biggest issue (in my opinion) with using aviation gas in cars is that it may be nearly impossible to start the car in cold weather. Automotive gas has a lot of lighter ends (propane, butane, etc) blended into it in colder weather to provide easy vaporization to start in cold weather. Airplanes can't tolerate easy vaporization as it would create problems at altitude (carburetor icing, vapor lock, etc). To overcome that, airplanes have fuel heaters to aid cold starts in cold weather.

Back in my drag racing days, aviation fuel worked wonderfully for me as long as I tuned for the higher octane. I usually mixed it with at least 25% automotive fuel to minimize the cold starting problem.

The second problem with aviation fuel in cars is the high price.

Also, those were back before unleaded fuel. I don't know if there is any lead in aviation fuel today. I know it has been reduced, but I don't know if it has been eliminated.

I don't know of any reason that you can't use it on your Mercury Marine engine other than the things mentioned above. I hope others speak up as well.

 

[SecondMonkey]

Yeah, there's still a little lead in it, but it's pretty low.

So I take it nobody thinks avgas can cause problems with carburetors or other rubber fuel system parts?

I'm not really too worried about performance right now...I'll just try it and see...but I don't want to hurt my engine.

 

[tom slick]

here is a little reading for you from last month
http://www.bobistheoilguy.com/forums/ubb...rue#Post1091711

 

[BuickGN]

Originally Posted By: SecondMonkey
I have a boat with a restored 1972 Mercury 150hp engine. These engines are notoriously picky about the fuel they drink. Mercury even lowered compression in later models due to the newer urine-like fuels.

Anyway, I was thinking about trying some 100LL avgas in the motor this year, mixed with regular 87 to around 95 octane. Partially because of the ethanol in regular gas, and partially because regular gas is garbage.

Anyway, will this cause any harm in a carbureted motor? My dad used to run it in his '67 Ford, but claims the "antifreeze" in the gas ruined his carb and apparently eats rubber. On the other hand he's really clueless about gas/oil and I doubt he has any idea what ruined his 40 year old carb...


It will cause absolutely no issues in your boat especially in the mixture you're doing.

I've run it straight in my car for nearly 7 years now. It will not hurt rubber components or any engine parts. Much better than detonating your engine.

 

[dwendt44]

Wouldn't it be just as effective and cheaper to run mid-grade?
Some stations around here have been charging the same price for the mid-grade as for the regular.

 

[SecondMonkey]

Originally Posted By: dwendt44
Wouldn't it be just as effective and cheaper to run mid-grade?
Some stations around here have been charging the same price for the mid-grade as for the regular.

I have to run premium 93 octane minimum, the more octane the better. I don't know if I'll end up using the avgas or not, depends on price, and how well it runs on the stuff. I'll probably try a tank or two though.

What I need to do now is calculate price wise, which is cheaper: 93 unleaded, 87 regular plus avgas, or 93 plus avgas.

 

[SecondMonkey]

Just so that I'm clear here - can somebody tell me what, if anything, is added to avgas as "antifreeze"?

 

[BuickGN]

I have my doubts av gas is rated using the normal average of RON and MON. I can run quite a bit more boost on 100LL than 100unleaded. Av gas most likely has more than 100 octane going by the normal rating. Over here it's usually about $1 more than premium.