Air Cooled outboard - fuel question

I was given a 5 hp Briggs & Stratton 5 hp 4 cycle recently. Have not taken it on the water yet but plan to hopefully on Sunday.

when I go and fuel up the tanks should I buy premium or are these engines not made for higher octane gas? Will it benefit the engine or no? It's basically a lawnmower engine made into an outboard motor. I think Briggs & Stratton quit producing boat motors, they are mainly a lawnmower company.

Just wondering if the high octane will give my engine a boost or if it's not worth the money or will more likely hurt the motor.... The gas will also be ethanol free, I know of a couple stations that sell it nearby.

Non ethanol fuel is usually 91 or 93 octane which is plenty high for stock motors. Ethanol is used as a cheap substitute to raise octane levels in fuel. The higher the octane level, the more resistant it is to premature detonation in the cylinder.

Exxon fuel is the best fuel to buy hands down!

We run premium gas in all of our air cooled engines along with Sta-Bil and an ounce of Seafoam per gallon of gas.

The few times that I have had catastrophic failures or had to tear into the engine, there has been very little carbon build up in the cylinders and the carbs have been clean.

Seriously, it's a 5 hp engine. It's not going to use that much gas even if you run it all stinkin day long. The cost difference in fuel is worth it in my mind.

On a 5hp engine, I don't think you'll see any difference with one vs the other, provided the motor will run with both which I think it would.

spotco2 said:

We run premium gas in all of our air cooled engines along with Sta-Bil and an ounce of Seafoam per gallon of gas.

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Just out of curiosity, since Seafoam functions as a stabilizer also, what is the purpose/advantage in running both additives in your fuel?

Just a habit I guess.

I've got several different cans that all get the same mix when filled. Sometimes a particular can might sit for several months before being used. Heck, some might even go a year before getting picked up. That's the main reason for the Sta-Bil.

The Seafoam we've always used for a cleaner.

Like you said, it is a 4cycle lawn mower engine, use the 87 octane (cheap stuff), keep the oil topped off, check and clean the plug once in a while. You will be fine.
Tim

A motor designed to run on 87 octane will actually make less power on 91/92 octane fuel. Your really just wasting money . Higher octane fuel actually burns slower to control pre ignition/detonation, so if you were to advance the timing or increase combustion it then benifit from the higher octane.