I was recently left in a "prop black hole" because I found out my Whirlwind 200RV prop will not be suitable for my IO-375 engine. I thought I'd found a solution with the WW-300 series, but it has some restrictions against non-counterweighted cranks (like mine).
I spent several hours today researching various props that would be suitable on my particular engine. Here are the only ones that will supposedly work (although I have not 100% verified the Hartzell is compatible with my crankshaft. I only know someone who is using it on his IO-375):
1. The Hartzell HC-C2YR-1BFP/F7497 two-blade, 74" composite prop (weighs 51.8 lbs), $15,790.
2. The MT MTV-9-B/183-50a three-blade, 74.8" composite prop (weighs 56 lbs), $15,500.
3. The new, unreleased Whirlwind 330-3B/72H-73 three-blade, 73" composite prop (weighs 53 lbs), $14,355.
There are literally no other props that are suitable, for one reason or another. It's always either horsepower limits, compression ratios, or crank requirements that kill them from contention.
The only other way I could proceed would be to upgrade my engine to a counterweighted crank, which would add 6 lbs and cost an unknown amount of time and money. Ugh.
I am leaning heavily toward the Whirlwind. I will be talking to them tomorrow for some more information.
(Early, test version of the Whirlwind 330 prop shown below for reference.)