Correct gasoline for 2006 250 HPDI Yamaha ?

[geodebasser]

I have been burning 100% gasoline but with the high cost I am tempted to go back to 10% ethanol and use a fuel additive? Another alternative would be to put in 10 gallons of 10% ethanol and 10 gallons of 100% gasoline. Would that be like 5% ethanol? My HPDI is running great right now but I realize it is a complicated motor that can be sensitive.

[tyfoford]

I run 89 in mine and have no issues. Yamaha manuals will tell you to run a minimum of 89 octane. I also run ring free and stabil with every fill up. I do only put 10 gallons in at a time and typically run those 10 gallons out after a couple of weeks. If you burn a lot of fuel, ethanol won't hurt. If you let it sit, that's when you will start to have problems.

That being said, if it were me, I would continue to run the higher fuel since you have been already. It costs more, but a new outboard or a repair are more expensive.

[SCOTT196]

I have the same motor, I would not use ethanol !

[MCIPinkie]

My standard answer:

Read the Owner's manual and follow it.

Pay no attention to what anyone, including me, tells you on the internet.

[yam911]

Owners manual is somewhat insufficient. Says to use 87 octane minimum.

OM does not address the benefits of using 89/91 octane given that HPDI's, for some unknown reason, do not have a knock sensor.

Is it just a coincidence that 3.3 liter blocks are known for suffering from detonation?

[CJ1]

Owners manual is somewhat insufficient. Says to use 87 octane minimum.

OM does not address the benefits of using 89/91 octane given that HPDI's, for some unknown reason, do not have a knock sensor.

Is it just a coincidence that 3.3 liter blocks are known for suffering from detonation?

Yall may want to listen to this^^^^. And remember the Yamaha SHO owners manual tells you the absolute worst way to break in a 4 stroke. I take care of 3 HPDI's 2 300's and 1 225. All run original pistons and have MANY hours on them with zero issues. I have personally seen what old or poor fuel does to these engines. I would not run anything less than FRESH 89 non ethanol in any HPDI let alone a 250 or modded 300's like we have. But hey, it's your money and engine. Want to roll the dice with 87? Go for it! CJ

[geodebasser]

Yall may want to listen to this^^^^. And remember the Yamaha SHO owners manual tells you the absolute worst way to break in a 4 stroke. I take care of 3 HPDI's 2 300's and 1 225. All run original pistons and have MANY hours on them with zero issues. I have personally seen what old or poor fuel does to these engines. I would not run anything less than FRESH 89 non ethanol in any HPDI let alone a 250 or modded 300's like we have. But hey, it's your money and engine. Want to roll the dice with 87? Go for it! CJ

I am going with your answer. Thanks

[CJ1]

I am going with your answer. Thanks

I'd just hate to see you loose a engine over $10 or even 100. I know that is what Yam911 is saying also. I know a very respected marine engine builder that lost a engine because of junk fuel. Sometimes you cant help it but you can sure do your best to prevent it.CJ

[Jer]

I alwayys use 91 fuel, no ethenol. Ring free in every tank. Mine is a 200 HP 2007 year. Runs perfect.

[Thamelau]

I can get behind running higher octane than the owner's manual states, but if you go through fuel regularly then there is no issue to avoid ethanol in a motor that has a manual that specifies an upper ethanol limit and you follow that limit. If you don't go through fuel often then I would avoid ethanol as well.

[CJ1]

I can get behind running higher octane than the owner's manual states, but if you go through fuel regularly then there is no issue to avoid ethanol in a motor that has a manual that specifies an upper ethanol limit and you follow that limit. If you don't go through fuel often then I would avoid ethanol as well.

I understand this thought process. And to be perfectly honest you will make the most HP with a fuel octane that is just above detonation. BUT when you run right at that edge you risk loosing a engine. Say you get 3/4 of a tank of last year's fuel mixed with a 1/4 tank of fresh from the local mom and pop gas station, your 89 is now 85. Add ethanol and that slug of water it collected just cost you #2 piston on your HPDI that was right on the edge for 89 anyway. Your waterpump is just a bit below what it normally puts out. That upper cylinder is now running hotter than normal, detonating with 89, another #2 burn down story. Ect, ect. To me a good safety margin allows me not to worry about loosing a engine. A good friend followed my advise when covid hit and mixed good fuel for both his outboards. They did not get ran for almost 2 years. Both ran fine all year. I suggested draining and putting in fresh but he didn't and still was ok. As far as ethanol, I would not go past 4 to 6 weeks without running it completely through the system. IMHO it is not worth the risk unless you are running every week at a minimum. Remember a percentage of old fuel remains in the tank unless it is ran completely dry. Cj