If you have a loader grate, and the shaft packing rings are worn out, it'll take water at higher speeds. At higher speeds (with a loader) you have positive pressure in front of the impeller. My 12 JG shaft seal will just barely drip at idle and low cruise, but drips much faster at high cruise or WOT. Still not a lot of water though, maybe 2-3 gallons during a full afternoon of hot-dogging around the lake. It sounds like yours is leaking pretty fast. Yes, it could be the bowl gasket, but I am more inclined to suspect the packing rings. Get someone to watch it (or drive) while you're romping on it. It's an easy fix, just add more rings. If the packing gland is tightened all the way down and it's still leaking, you'll probably need to add 2 rings.