Never heard of them, but that goes for all V Drives
As for the Prop. Diameter and Pitch are usually stamped somewhere on the Hub. A Prop Rebuilder, would have the Tools needed to measure things like Rake and Cup
Some Diligence has to be used, as mixing some parts will result in an Engine's Demise. Pistons, Rods, Cylinder Heads, and Crankshafts are different between the 18/20hp and the 25hp versions,
If it was an Optimax, using premix, would have destroyed the engine in a few minutes, or even quicker, when the Motor's Oil tank ran dry. The Crankcase only sees Air, and injected oil, not Air, Gas, and Oil like a regular 2 Stroke
"@ 80% of WOT"
What do they turn at WOT? That is the Number that matters. 80% of Throttle Lever Movement is meaningless, as the Throttle Lever is not Linear to Rpm.
Since you have doubts about the Tachometer Accuracy, then that should be the Priority. Verify that it is set correctly, if it is...
Wood is the Weak Link in Transom Longevity. Marine Grade Plywood is still Superior to Exterior Grade. Don't let anyone convince you they are the same, as they are not.
