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Question on 2 to 1 gearbox and what pitch to use

Frank Finlin

Well-known member
I have a question, I melted two pistons in my old Z350 engine and the engine gave me problems that nobody was able to solve.

So I decided to have a total new engine built, the builder worked with Panther Airboat.
I’m operating a 14 by 8 airboat. Panther felt that a Z502 would be too heavy. So I settled on a Dart block 420 cu in with Eagle crank and connect rods with J&E pistons, running Brodix heads with roller cam with solid lifter ground to develop good torque range through 5000 rpm.

I was running a warp drive 6 bladed propeller with 2 to 1 gearbox. Panther recommended going to an 8 Turbo hub. The engine dynoded out at 550 hp 510 ft lb torque.

After reading some of you comments about 2 to 1 gearbox with a high degree of pitch stating that this is extremely hard on the engine, what pitch range would you recommend the propeller is 84” diameter. If I run the engine at 5300 rpm would this work keeping the engine strain down or should I change the gearbox?
FMF
 
Frank, you and I are in the same spot. I run a 2:1 belt and if the truth be told we're both lugging our engine unmercifaly without a bigger gear.

I don't have the rigging to let me run a prop that a 2.68 would let me turn, but I'm definitely looking for more reduction.
I think you should too, in my opinion.
 
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