I have found legit non ethanol fuel rated at 90 octane, that I could put in my 292 Fastech. So, my boat has little 320 hp 6.2l sbc, with catalyst exhaust. The engines are rated for 87 octane, and I understand that extra octane in an engine not designed for it, is not helpful.

I move enough fuel through the boat so I don't have to worry about the fuel going bad, I am looking for opinions on any potential performance impact.

So....
will this help or hurt hp?

Will this help or hurt anything else?

Cost is my last concern....it is just boating. Fuel is the cheapest part of the equation. Non ethanol 90 octane is $2.95 vs $2.25 per gallon if that is an issue to consider.

Wait for the guys that know but if it's leaded it'll be bad for the cats. :-)

It won't be leaded fuel. The only fuel with lead are AV and high octane race fuel.

I run ethanol in all my vehicles, but never in the boat anymore. Its attracts moisture and it also causes my engines to vapor lock.

I can get non ethanol 87 on land here. Its about $.30 more than E10.

If you burn through your fuel often and always top off with fresh I don't believe you will benifit any reliability nor performance, but you will waste money, time and might lose power with the 90 Non Ethonol. Biggest benifit of the 90 Non Ethonol is false peace of mind....Unless your fuel is stored for longer periods without stabilizer.

Great question though!

I fill up on the street. So, I've been running fuel with ethanol for MANY years. Knock on wood, never any fuel related issues in any of my boats.

what ever you decide run either one or the other exclusively. There are additives in each that do not play well with each other so switching back and forth and blending them is not a good idea unless you run it dry each time and eve then I'd be concerned about the residual.

Corn is for Chickens and Pigs

...and Bourbon

OP, I assume your engine is circa 2014 like your boat and if you're using it enough ethanol should be fine. I have a 1996, when ethanol blends weren't available yet, thus hardware that isn't compatible. I run non-ethanol fuel as a result for peace of mind.

Keith