Slow speed vs Fast foodI suspect the problem here is too many Happy MealsFact is, I would never expect a 15hp to pull a tube except maybe for a kidIt is just too small.
There is only one problem, you're too heavy for the hp output of the motorYou need to have at least a 35 hp outboard motorIf you increase the surface tension by getting a larger tube, all you'll be doing is going slowerWhat you want is a tube with the least amount of surface area touching the waterThe same theory applies to boats alsoThe only instance when a wet surface area makes little difference is in a Displacement HullThe thing with this hull is that it won't plane , nor be very fast.
A time machine!!!.Or.as the other well informed have stated.on a horse called Sundae.no.that's an ice-cream.I mean Sunday!!
