91 octane ethanol free vs 93 octane w/ 10% ehtanol for SVHO

[jdbakerucf]

So does anyone have any experience or recommendations on fuel type for the SVHO engines. I have access to both 91 octane (corn free) and the standard 93 octane. I know the SVHO engines are supposed to run 91+, but I was wondering if there would be a benefit of running one vs the other. In my area I believe the 91 octane is about 20 cents cheaper, but I was thinking the higher octane might be better in the hot FL summer weather (water and air temps above 90). Any thoughts, experience or recommendations are greatly appreciated.

 

[GTBRMC]

I would definitely choose the corn-free 91. It meets the octane requirement from the builder (and unlike a lot of popular belief more octane does not necessarily mean better performance) plus none of the marine-use downside* that comes with ethanol. And it is cheaper. Win-win.

*Ethanol is hard on your engines seals and other non-metal materials. Any engine built in the last few years, however, is engineered and built with understanding that it will likely see ethanol blended gas, so this is not nearly the problem that it was years ago. OTOH, ethanol IS hygroscopic - so it will pull water out of humid air and into your fuel. This is a significant issue in humid areas (lakes or oceans) and Florida certainly has a lot of humidity.

 

[Tayhadasuperjet]

My theory - I use ethanol free when I can, but especially at end of season so that is the fuel I winterize with. My boat stays on the water with no access to a gas station on the water. So throughout the summer I do use Premium (with ethanol) because of convenience to my house.

I don't have humidity issues being in the northwest so I think that also plays into it.

 

[Canuckjetboater]

Ethanol should not touch an SVHO engine.

 

[Tayhadasuperjet]

Ethanol should not touch an SVHO engine.

Based on what? I agree that it is not a preference, but ethanol has a higher detonation point, etc. If anything ethanol is safer than non-ethanol for forced induction.

Back in my Subaru days, the best power outputs on those engines were from E-85

 

[Canuckjetboater]

Based on what? I agree that it is not a preference, but ethanol has a higher detonation point, etc. If anything ethanol is safer than non-ethanol for forced induction.

Back in my Subaru days, the best power outputs on those engines were from E-85

Recommended to NOT use by Mercruiser, Volvo/Penta and Yamaha. Each of the manufacturers will provide a list of reasons. For my boating friends and I it is our opinion: Ethanol (I even hate to type that word - geez we just gag on the word we hate that $hit so much)...,.,.Less "energy dense" depending on whose data you believe provides (on a per gallon comparison) 20-33% less power. Pulls (under load such as towing) 20% less power. Significantly reduces distance travelled. Induces vapor lock. Pitts fuel rails and injectors. Deteriorates marine components prematurely. Should be generally considered as $hit for your marine engine and a waste of money for your land vehicle unless you are a corn farmer or have drunk the cool-aid from the corn lobby. Oh yeah, and the crap attracts water. We ask for Marine 91 which is ethanol free - most particularly for supercharged engines like the Yamaha SVHO and marine high performance engines. Oh, yeah, and that crap attracts water.