That is a good point regarding what RPM level the HP was achieved. Torque is important, but I think again you have to consider at what RPM level it was acheived.

Although a V-6 will tow such a boat, if you want your vehicle to last a long time the less it works the better. I know someone who has the 4.6L in an F-150 and he claims he gets 20-22 highway with it.