Re: Best Fuel for older motor
I have a 1974 Johnson 115 hp. The owners manual only calls out to use Leaded Gas, nothing about octane. Fuels have changed since 1974 and locally I can only purchase fuel with 10% ehtenol. I know that for my SST-45Tunnel Hull race motor we have better performance with the lower octane fuel. Does this hold true for my 1974 115 hp also? What is the best octane fuel for performance and to keep the engine clean internally? Thanks
I sure wish I still had all the details, but they had fuel problems back then. The horsepower race was on just as the leaded fuel was outlawed. Motors were destructing from pre-ignition and detonation. There were several service bulletins about changing carb jets and timing to prevent it.
Anyhoo, some motors even called for Premium Leaded Gas to get enough octane. Is that what your owner's manual says? If you ask BRP about it now, they will give you some line of BS. They weren't there at the time.
This info is for whatever it is worth. I don't know the answer to the direct question, except to say be sure you have octane that is high enough---whatever that is. I don't have one, but if I did, I think I would be running at least mid-grade. Just my 2c.
EDIT: When they took the lead out, I got stuck with two cars requiring premium leaded. A Pontiac Bonneville and a Corvair 110hp. The Corvair wouldn't even run downhill without pinging. Even with the timing way retarded. The Pontiac wasn't much better.
