89 octane

Just bought a new WX2060 with the 250SHO. This engine will run on 87 octane but it is recommended that 89 octane be used for best performance. Where I live, 87 octane and 91 octane fuels are available but 89 octane is not. Conventional wisdom tells me that I can use a 50/50 blend of 87 and 91 octane and get the needed 89 octane. Am I correct or does the math on octane work differently? This is probably a stupid question but I have been surprised before.

I will be interested in this as well as I will be running the F200 this year that requires 89. My understanding is you must run a minimum of 89, so you can use the 91. Someone would need to confirm this however.

89 is the minimum that you will want to run. Running 91 is fine and you will get full performance out of it.

If only 87 and 91 are available around you I would suggest to use just 91 and don’t mix it with 87.

What about fuels with ethanol added? I try and avoid that stuff for everything regardless of statements that it is not harmful to an engine.

Dave Lozier wrote:

What about fuels with ethanol added? I try and avoid that stuff for everything regardless of statements that it is not harmful to an engine.

The engines are designed to run on up to 10% ethanol. Where it will start to hurt the engine is when the fuel itself breaks down. If used regularly and not allowed to get old you should have no issues.

The other reason to fish more “honey but the gas is getting old I have to go burn it up”

and you’re off an running

Eric Rehberg wrote:

89 is the minimum that you will want to run. Running 91 is fine and you will get full performance out of it.

If only 87 and 91 are available around you I would suggest to use just 91 and don’t mix it with 87.

I’m with Eric. Stick with 91 octane. Most 91 octane that I have seen is non-oxygenated (no ethanol).

The SHO 250 is rated for minimum 89 octance. So I would never put 87 in it. The Offshore 250 can run 87 octance and my dad does most the time. With my 300 Offshore if I can get it I run 89 octance but I also always run Ring Free and Fuel Conditioner.(Yamaha products).

I think my boat runs better on 89 then 91. I know the ProXS guys will say the same thing.