I have a 1992 Seafarer with a 1993 Yamaha 225 on an engine bracket. I'm only getting 4100 RPM at best at WOP. That's about 28-29MPH. The engine seems to run really well and it does plane nicely. The manual says I should get 5000-6000 RPM. My stainless steel prop is a 14 1/2 - 17. Do I need...