Type of Gas

[jester]

So in the owners manual it says to use 89 oct for gas. Has anyone found an issue using 91? Good bad anything?

[Razzman]

Not that i know of but as it's more money why would you? Unless of course that's all you can get. You'll not benefit from using it really as everything is modulated by the fuel injection system, it's designed to work with 89 if i remember correctly. IMO mine runs perfectly with 89 so i'm not about to mess with it.

[Trashy]

Run 89 if you are using your boat weekly. If it's going to be a while before you use your boat again use 91 so the octane stays above 89.

[sandm]

always use the lowest octane recommended. no benefit to running any higher octane unless your engine is high compression or boosted. higher octane just prevents detonation as it burns differently.

now ethanol blended is another story. that crap sucks in our boats...
vaporlock ftl..

[jester]

Well my thing is i have a gas station that sells only 85 and 91. I can get the 91 for less then i can get the 85 at other gas stations. Have to love Costco. I have never had an issue running their gas in my cars so was thinking about starting to run their 91 in my boat. It will save me about 30 cents a gallon.

sandm,

I know what you mean about that bad ethanol. do they not understand that a 10% ethanol blend will give you about 10% less gas mileage. In Oregon it is law to have at least a 10% ethanol. The bad thing is older boats started to explode because the ethanol degraded the fuel lines and caused leeks.

[sandm]

there are 2 issues with ethanol, first being a decrease in fuel economy, and second with the boiling point of fuel blended with ethanol. in the heat of the summer with the enclosed engine compartments, vapor lock has been an ongoing issue for several brands of boats and a couple makes of cars with so much plastic and no fresh air flow.

if you have a flexfuel vehicle, there are other issues if you run regular gas, then switch to e-85 after 30-40k miles, it stirs up all the dirt/sediment in the tank and flushes it though the system. and lets not even talk about gov't subsidies on the product from the cornfields to the pumps...

e-85 has a strong following in the boosted import car scene though. e85 is a very high octane fuel and can be had for a cheap price. lots of guys I know running it in high-psi boosted cars and seeing large hp gains for "free".

your boat should run fine on 85 though. I've ran it and not had any issues with it.

[deerfield]

jester - From the Indmar Marine Engine Owner Manual:

1) All Indmar carbureted and standard EFI engines run on unleaded fuel of 89 octane or higher.
2) Indmar recommends purchasing fuel from a supplier that advertises that the fuel meets "TOP TIER" specifications with higher quality additives to reduce build up of deposits on fuel injectors and intake valves.
3) Indmar recommends the regular use of Sta-Bil fuel stabilizer for boat users that consume less than a tank of fuel every two weeks.
4) Fuel that is no more than 15% methyl butyl tertiary ether ("MBTE") is acceptable for use in an Indmar engine. MBTE is an oxygenate and octane enhancer.
5) Ethyl alcohol, ethanol, or grain alcohol is acceptable as long as it is a blend and the blended fuel contains no more than 10% ethanol.
6) DO NOT use fuels that are blended to contain methanol or wood alcohol in an Indmar engine.

Bottom line, stick with the 91 octane. Given your two choices, that is the only one that meets Indmar's requirement for warranty and optimal operation.

Hope this helps. - Deerfield

[Trashy]

I work at Costco, so understandably I use 91 in my boat and I have never had an issue with their gas.