If fuel gets to $5-6 a gallon, it might have some effect.

People go boating knowing full well that the entire activity is
expensive and cannot be justified financially from *any* perspective.
If $100 a day for fuel becomes $150 a day, or even $200- very few
people will stop boating as a result. After all, with $1000/month boat
payments going out 12 months a year who is going to let a few hundred
extra per month for fuel keep them ashore during the prime boating
season?

I do believe that high fuel prices will have some effect on the *type*
of boats that people will buy. For the last decade or so, the only
thing peole have cared much about is "how fast will it go?" I think
more buyers are likely to begin considering fuel economy as well as
speed when choosing boats, engines, etc.