What gas in 340 HP Indmar?

[Bluesman]

We just bought a new 2005 Mobius with the 340 HP 350 motor. The salesman said to use 91 because it's the 340 motor. Looking at the book, all the 350's for Moomba are 9.4 to 1 compression. Since they have the same compression I don't know why this one motor would need 91 gas.

Does anybody know the right info on this?

[mobiusLSV05]

My 05 325hp/350 will only take premium, at least thats all Ive given her to eat(175.00at 2.79) in three days and 16 hrs of hard use. Use what you want, but the higher the octane the hotter and cleaner it burns.

[NC05LSV]

That is the first time that I have heard that you had to use premium in any of the engines. All that I have read says use minimum of 89 Octane but doesnt reccomend anything higher than that.

[clark]

I also have an 05 Mobius, and my manual also says run 89 octane. However, with the rising gas prices, I contacted INDMAR, and told them exactly which engine I had and here is there response:

Good, fresh 87 octane fuel will be just fine. I suggest buying fuel in small
quantities so you do not have a full tank of fuel sitting around for more
than a couple of weeks. Fuel degrades over time and in a couple of weeks,
that 87 octane fuel may not be 87 octane any more and that's when you may
have problems. That's why we recommend 89 octane because if it sits around
for a couple of weeks it will still be equivalent to 87 octane, which will
not hurt your engine. If you do have fuel that stays in the tank for more
than a couple of weeks, we recommend that you add a fuel stabilizer, such as
Sta-Bil to keep the fuel as fresh as possible.

When I was on vacation for a week, I only ran 87 octane and my boat ran fine.

Clark

[Buttafewcoe]

I wonder if octane booster would be of any benefit?