Whirlwind?
Ron,
IMHO, you might also consider the constant-speed Whirlwind 200RV propeller. Here's the link to Randy Lervold's Hartzell vs. Whirlwind propeller testing:
http://www.romeolima.com/RV8/Prop.htm
Randy didn't test the MT, though.
I have a friend, Robert Paisley, who has a three-blade, variable-pitch (electrically-controlled) MT propeller installed on his really nice Eggenfellner-Subaru-powered RV-7. His RV-7 is one of the fastest RVs in Southern California. That being said, Robert says that if you elect to install an MT, he recommends that you order a narrower-chord model than what MT conservatively recommends for a 200hp engine. He found that he was over-propped with MT's originally-recommended propeller. He thought the propeller was more suitable for a 260hp engine.
Robert switched to a narrower-chord MT model and literally took off! I suspect that some of the reported MT performance issues result from a mismatch between the MT prop, engine, and RV. With the right MT propeller, it appears that the MT is competitive, in terms of performance, with both the Hartzell and Whirlwind propellers. I'm sorry that I don't have Robert's MT model numbers for you, but I know Robert occasionally monitors these forums and is a member of the SoCAL RV List on Yahoo, so you should be able to contact him if you're interested.
One thought: After flying in Robert's RV-7 which has a well-balanced MT propeller/Subaru engine combination, I can say that I've never flown in a smoother-running RV. I've flown in several terrific RVs with Lycomings and Hartzells, but it's like riding on a Harley (Lycoming/Hartzell) versus a Honda Gold Wing (Subaru/MT). I suppose if you're a "Harley Guy," you'll like the Lycoming/Hartzell; if you're a "Cruiser," you'll like the Subaru/MT. That's not to say that Lycoming/Hartzells aren't smooth; it's just that Subarus/MTs are smoother. One more thought: A three-blade prop like the MT on Robert's RV-7 simply looks good - - There's no denying that!
Since I'm building an RV-8A to be powered by a relatively heavy 200hp, angle-valve Lycoming, I'm leaning toward the Whirlwind 200RV, mainly to save 18 pounds on the nose versus the nice, but heavier, blended-airfoil Hartzell. That being said, if I were installing a lighter 180hp, parallel-valve Lycoming in an RV-8 or 8A (or my 8A's "as built" weight and balance turns out to be different than I expect), I'd be installing a Hartzell. Note: For an RV-7, it may be best, for weight-and-balance reasons, to have a relatively heavy Hartzell up-front - - you should check this out with the RV-7 community.
I have also been tempted to purchase the MT as well, since it's a well-proven certified design, but the Whirlwind 200RV (with McCauley hub) appears to be a better value, and the 200RV is now past its initial teething issues (cracking spinner bulkheads, as I recall - - the blades and hub have been fine). Personally, and excepting variable-pitch versus fixed-pitch performance differences, I don't think there's all that much difference in propeller performance if you achieve the right propeller/engine/RV match. I would suggest that weight and balance, plus price, are possibly bigger factors in propeller selection than relative performance. That's just my personal opinion, though. Bottom Line (as always): Select the one you like!
Best Regards,
Bill Palmer