It'll all come down to the set up... What heads, cam, timing...  Talk to the guy you are purchasing it from but you're probably going to have to run race gas with that much compression.

If you can't get any history from the seller, I'd suggest start with 110, and try coming down until you start melting parts.  Then you'll know where you need to be 

Welcome to SCJB 

Good call...

Sounds like a good candidate for E85 too....

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Be where I'd be at. But Avgas should be fine in it, there are different octanes for that too and get the highest one, I would say 108 or better. If it's an open cooling jet boat, you can get away with more compression (and boost on a blown engine) than normal, so that should be fine.

E-85 would be tits, if you can get it locally....Proppy just informed me a gas station down the street from even him (In the middle of nowhere) just started selling it.........

RAy

just dump a can of this into your gas tank

just dump a can of this into your gas tank

Really? Why?

sent from my mobile wireless thingy

I'd run c16 or if you can afford it q16 from vp. Sp13 is what allesie at boost power runs thru his big power motors