Here is an excellent review of the Yamaha Nytro Power: https://amsnow.com/news/dyno-tests/2007/08/dyno-test-yamaha-fx-nytro
Peak HP is at 8500 rpm, while peak torque is at 7100 rpm according to the article.
When I was building my Tango and running thrust test we came up with 8200 rpm as the max rpm setting in the air by adjusting pitch in the Luga props. Considering that torque is more important for climb, would adding pitch help in a climb? Normally, more pitch in the prop equals better cruise and less pitch with higher rpms equals better climb.
I am currently running a 4 blade Bolly Prop and without test pounds of thrust on the ground attempting to find the sweet spot for climb and cruise. I was running it at 8200 to 8300 rpm on climb out at 65 mph. As airspeed increased so did the rpms, something I did not see with the Luga, NR or Aero props. At 75 mph it would increase to around 8500 rpm. Above 85 mph it would increase rpms up to 8800.
Yesterday, I added less than a degree of pitch with these results, 8100 rpm at 65 mph, 8300 at 75 mph and 8600-8700 above 85 mph.
When I conducted the test flight density altitude was very high and I did not see significant changes either direction in climb performance and did not fly long enough to check fuel burn at cruise. More to follow.
Danita and I took a late flight a little while ago. Temperature was around 83 degrees and very light winds. We had around 12 gallons of fuel and our gross weight was 1050 lbs. Best climb rate at 65 mph and full throttle just short of 8100 was almost 500 fpm. At 7800 rpm we were still climbing at about 400 fpm. Sustained cruise at 70-75 mph was at 7400-7500 rpm. Temps during the flight stayed between 145 and 147 degrees.
We both noticed how smooth the engine was running. I really think that the head gasket had a minor leak for a long period of time, probably causing the impeller to eventually fail.
Please comment on the following from the manufacturer: Match Your Propeller to Your Engine Power for Maximum Performance and Economy
Set the blade pitch angle to fully load your engine when at full throttle, either up to the engine redline rpm, or up to 100 or 200 rpm below the engine rpm redline, when at full power. If for an aircraft, set the maximum full power rpm for when flying straight and level at your typical cruising altitude. If for a boat, set blade pitch for when up on plane (or as fast as the boat can go) in smooth, calm waters at full throttle, at or just below the engine redline. Obviously you will need a tachometer connected to your engine. This procedure applies to ALLengines turning propellers to produce maximum THRUST using the available engine power you have! This also makes your propeller act as an rpm "governor" for your engine, limiting full throttle engine rpm to its maximum safe setting.
best explanation of prop setup I have heard to date. Short, concise and effective.