As others have mentioned, jet boats are intrinsically less-efficient
than prop boats. Additionally, 2 Cycle engines typically consume more
fuel than 4 cycle engines and there is the added cost of oil. Also, in
my parts, some lakes are banning 2 Cycle engines that are not direct
injected. Last, I find I/O's very manuverable boats with little throttle
needed (idle) to navigate at low speeds in docking situations.

b.