I am running a Mercruiser 500HP with a Procharger and intercooler setup. Fuel is a BIG issue and unfortunately you can't purchase high grade (92 octane +) on the water. I always fill up at a fuel station when it is on the trailer, but does anyone have a recommendation as to what brand of OCTANE BOOST to use for when I need to fuel up on the water????? I want to make sure I am using a high quality/well performing brand. Thanks!

Octane booster isn't effective you may be able to up it a fraction of a point like from 87 to 87.2 or some such number. Your best bet is either mix with a much higher octane fuel or try one of the home octane booster mix like toluene and some oil, I can't remember the mix but it is available on the net at a number of sites.

Octane booster won't work for you.

1 gallon of 110 plus 3 gallons of 87 put you just under a 93 octane rating.

I have same problem. I have a 10.5-1 Pfaff motor
which need more than 92. Normally I mix 2 gal 110
to 30 gal 92. Mathamaticaly this cal. to 93.125,
but the R/M factor of octane rating increases
at different rates, thus you would have a greater
octane that calculated.
What I do if I will be on the water for days is double
the amount of 110, burn 1/2 tank then refuel. This
keeps me at a safe octane. Beings you can only get 87 though add more 110 or pack some with you.
Hope that helps.
GEO

Thanks for the advise!!!! I guess that is what I will have to do......