Shipyard Isl. Marine Engine Parts - Fuel Octane Question

I have a 2004 Yamaha 150 4-stroke. The owners manual states that a miniumum of 86 octane fuel is required. I have been using 87 octane E-10 fuel. Recently, a few service stations startes selling non-ethanol fuel but they only do it at 1 pump and you only have the choice of the octane level they sell at that one pump.

At first they offered 89 octane. Now they have upped it to 93 octane. I put 20 gallons of the 89 octane in it and noticed no problems. After I ran that down, I added 20 gallons of the 93 octane in it and noticed no problems.

I don't mind paying the extra money because it is ethanol free. My question - Is there any harm in running 93 octane non-ethanol fuel? When the end of the season comes I'd like to fill it with the non-ethanol fuel if there is no problem doing this. I have a 90 gallon tank.

You can run 93 octane if you want, but its not necessary. I would try to stick with either Ethanol fuel, or non Ethanol.

We have 91 octane non-ethanol here at our place, and I can't ever recall ever having a local customer that uses our fuel ever having a fuel issue. We have customers with fuel issues that we service, but its fuel bought at other places.

Andy

Thanks for the info. I'll stick with the non-ethanol fuel as long as I have that option.

As you pointed out, "The owners manual states that a minimum of 86 octane fuel is required."

Minimum is minimum. There is no maximum octane specified. Last time I checked, 93 octane exceeds the minimum requirement of 86 octane.

What harm do you think would come if you exceeded the minimum of 86 by 7 points versus exceeding the minimum by 1 point. Or, three points in the case of 89 octane or 5 points in the case of 91 octane? Other than financial harm that is.

As you pointed out, "The owners manual states that a minimum of 86 octane fuel is required."

Minimum is minimum. There is no maximum octane specified. Last time I checked, 93 octane exceeds the minimum requirement of 86 octane.

What harm do you think would come if you exceeded the minimum of 86 by 7 points versus exceeding the minimum by 1 point. Or, three points in the case of 89 octane or 5 points in the case of 91 octane? Other than financial harm that is.

A few years ago the company that serviced my boat said they did not recommend putting anything higher than 87 octane in as it wasn't good for the engine. I never asked why it wasn't good as I could always find 87 octane that did not have ethanol in it. Last year was the first year I could not find ethanol free gas at a Marina or gas station so I used 87 octance E-10.

Last year was the first time my engine started sputtering, losing power, etc and I ended up having clogged injectors. Just last month, the non-ethanol gas became available in 89 octane and then they bumped it up to 93. Before I commit to filling my 90 gallon tank at the end of the season I just wanted to run a quick question out there to make sure there would be no harm. I appreciate your input.

A lower compresion motor may have poor cold starts and stalling cold on high octane fuel.