(46 hp x 5252)/2000 = 120.8 ft-lb torque. As JimC said, that's not counting any frictional losses in the gearbox.


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"So I guess I need to know prop HP to calculate prop torque?"

No, but you do have to apply the gearbox losses while computing it (they can be substantial).
Why would prop torque be of interest unless computing hub or prop bolt dimensions?

"For what its worth. Engine HP is 46 at 6000 RPM and 41 ft/lb of torque".

That's worth quite a bit because those numbers don't jive. If horsepower is 46 at 6000, then torque isn't 41. And if torque is 41 at 6000, then horsepower isn't 46.
Close, but no cigar.

JimC wrote:"So I guess I need to know prop HP to calculate prop torque?"

No, but you do have to apply the gearbox losses while computing it (they can be substantial).
Why would prop torque be of interest unless computing hub or prop bolt dimensions?

"For what its worth. Engine HP is 46 at 6000 RPM and 41 ft/lb of torque".

That's worth quite a bit because those numbers don't jive. If horsepower is 46 at 6000, then torque isn't 41. And if torque is 41 at 6000, then horsepower isn't 46.
Close, but no cigar.

That's as close as I could come reading the tiny Rotax HP/Torque graphs and converting NM to Ft/LB and KW to HP. Heck, Rotax doesn't even know the difference between a coma and a decimal point.

I'm having trouble understanding the formula. At 6000 RPM and 46 HP what torque do you get, and what Hp if torque is 41 at 6000 rpm? How close is needed to get a cigar?

Okay, after some closer looking I have figured it out. Thanks for the help.

"Rotax doesn't even know the difference between a coma and a decimal point".

I expect they do. Rotax is based in Austria, and in Europe, decimal poits are commas, not periods.