jet drive ,drive line

Hello: I have an amphibious vehicle project started ( 20 ft aluminium cat hull ,with wheels tucked in the sponsons) the drive line is to use an auto (jeep) dana18 transfer case powered by v8 to drive the jet drive. the transfercase was reversed so the old input(reardrive is now the output & the old input now is to drive jet pump) the question is if the transfercase is shifted into low it now is spinning 2to1 faster (like an overdrive, the the low gear has half the teeth) should work great in high gear(1to!}.the 2to1 may be to high and would require more H.P. and torque?

 

May Be........complex problem with no easy answer. Without drag curves for the hull, power output curves for the engine, and a thrust map for the jet.....no one can say.

The usual critical point for jets is at "hump" speed, trying to get up to planing speed. But this may not be a planing hull? There may be a small or non-existent hump in the resistance. What sort of speed are you intending? And can the jet produce the thrust to attain that speed?

 

amphibian

Thanks for response> it is a semi planing hull with some drag from rear wheel wells,the wheels will retract a little. about 9 inch of draft underway 12 idle. the jet drive should handle weight and require about 225 H.P. at 3000 rpm to get a plane (there figures) .ii tried to send data to your sites, did not seem to work/