If you had 10.5CR with iron heads, I doubt it would be alive right now without running at least 93 octane.

That's what I've always been told. I know some guys that were running it in their race cars and they had problems with it. Maybe mixing it with regular gas helps, but I would tend to think that you'd be better off using a Torquo 108 or something like that, opposed to an airplane fuel that has additives that aren't needed in a marine application.

NO.....ethonal or alcohol are not present in AVGAS, that would be a big problem, as they would boil at altitude causing fuel starvation problems, not a good thing at 5000 ft. Its actually a very good alternative to race gas if you dont need over 100 octane. It does have a small amount of lead in it, and will screw up any 02 sensors if you are running them. The subject has been beat to death on here, whether its ok to run. I have run it in many motors 2 and 4 stroke and never had a problem. The problem is buying it. Not every airport will sell it to you.

10.5 to 1 and steel heads combined with 87 octane=blown motor/burnt pistons.

With that high of a compression ratio and steel heads, you should use nothing less than 93 octane.

So back to the oringinal question, what to do??

Fill up BEFORE you get to the ramp !!!!!!! :confused::confused:

Good answer. But for arguments sake, like here and other places, I can't fill up on the road, what's to do??

The only concentrated octane booster that would be relatively simple to carry on the boat is the Torco Accelerator. It is very expensive though. It looks like 64oz would give 40 gallons another 4 octane points.
http://torcoracefuel.net/pro-accelerator.html

If the boat is in the water and you will need something on a regular basis, I would get 55 gallon drum of race fuel or Toluene. 32 gallons of 87 octane and 8 gallons of Toluene(114 octane) will get you about 92.5 octane.