2005 vmax 200 ox66 what octane fuel

[kram31]

I have run this motor for one year and have always put ethanol free 91 in it. Ive always ran 91 in all my outboards but im now reading i could do damage to the motor? motor compression was strong when purchased at 117-121. Is it safe for me to run 91 or should i be running 87? marinas on the lake only serve 91 ethanol free.

[21XDC]

87 for a stock motor... I run 89+ min as I have shaved heads.

[kram31]

So i should no longer run 91 and switch to 87? is it possible I did serious damage to the internals? I put 25 hours on it running 91

[1ranger487vs]

I have same motor and I always run 89 with ring free

[yam911]

Higher than normal octane will not harm the motor. At all. Yamaha says to use 86 minimum in your model. Minimum as in no less. But more is just fine. Except for your wallet.

[yam911]

Between a choice of 86 octane with 10% ethanol and 91 octane with 0% ethanol, the motor makers will suggest the latter.

[kram31]

91 is the only easily attainable fuel that is ethanol free. Ill continue to run 91 with ring free unless I come across ethanol free 87 here and there. I don't mind paying an extra 20 cents a litre. Thanks for the input!

[1ranger487vs]

I use 89 with 10%ethonal always have. But my rig doesn’t sit more than a few weeks

[OverTimeAgain]

Higher octane will just carbon up your motor faster. I think you're just supposed to do some maintenance items more frequently. Spark plugs and oxygen sensor are the only things that come to mind.

[yam911]

I am somewhat familiar with Yamaha data and there is no mention that I can find of any Yamaha guidance that addresses the need for more maintenance if and when using gasoline with a higher octane rating. Have not been able to find any data from any of the other motor makers that mention this either.

Many additives can be used to increase the octane grade of gasoline. Ethanol being just one. The evil one. Ethanol is stated as burning more cleanly than straight gasoline. But I don't know for sure.

[wcs69rat]

21XDC,

Do you know how much they milled off of your heads and what your average compression reading is? I was thinking about sending my heads to HydroTec to have them milled or have a local shop do it. I have a 2004 225 OX66 that is stock. I currently run 90 octane ethanol free, but I do not have an issue running 93 octane (however, it would not be ethanol free). Was there a noticeable difference when you milled the heads and do you have any idea how much HP you gained?

Thank you.

[21XDC]

21XDC,

Do you know how much they milled off of your heads and what your average compression reading is? I was thinking about sending my heads to HydroTec to have them milled or have a local shop do it. I have a 2004 225 OX66 that is stock. I currently run 90 octane ethanol free, but I do not have an issue running 93 octane (however, it would not be ethanol free). Was there a noticeable difference when you milled the heads and do you have any idea how much HP you gained?

Thank you.

Stock is 115-120lbs compression on my 250... I think I'm at 135lbs now. I have a snapier holeshot and acceleration. Only 1-2 mph on top end. HT wont tell you how much was shaved.

[wcs69rat]

21XDC,

Thanks for the info. I'm more interested in the hole shot and acceleration than top end. If I pick up a couple MPH, that's just a plus.

[21XDC]

The lightweight flywheel also helps some on holeshot and acceleration.

Gains will differ on different hulls... Lighter hulls gain more ofcoarse.