Hello. I bought a 99 nitro 185 sport with a 120 2 cycle force mercury. My concern is when I am taking off it revs under load to 3500 then shoots to 5500 with no more thrust. It does not slow down, its still accelerating but just not any different. It does take a bit to plane out. The best way I can describe it if the prop is pulling in air allowing the load to decrease and the engine to rev. Once it planes out the rpm drops to say 4800 and you are running 30 with about 10 more to go before it maxes out. I (not knowing boats that well) was thinking a dolphin tail might help if it is in fact pulling air into the prop. Anyone have any good suggestions? Or what I might do to test it.