I have a type III with a Subaru EA81 engine and a 1.80:1 reduction drive. The engine is rated at 80 HP at 5,000 RPM. The max RPM I've seen is 4,000. Since I didn't build the airplane, I have no knowledge as to how this came to be. The question is, should I just simply adjust the prop until I get the 5,000, or are their other things that I should consider?

Thanks, I'll standby for your comments.