rathrbfishin
Cadet
- Joined
- Apr 15, 2004
- Messages
- 14
I have a 18ft CC bay boat with an 90hp yamaha. I had a SS 17pitch prop which was running 5900rpm @ wot. I change to a SS 19 pitch because I was over my recommended rpm range. I thought that the 19 would drop my rpm's to around 5500 and I would gain a little more top end , but instead dropped them down to 5000rpms and made me even slower than before. My question is if i change to a 19 pitch aluminum prop , will that increase my rpm's and top end. I went from 41mph with the 17 to 33 with the 19. When I changed to the 19 pitch my motor was mounted all the way down (running 4800rpm's) raised to about 1.5" above bottom of boat , that when I started getting around 5000 rpms. It just seemed like a drastic drop in rpm's from the 17 to the 19 pitch. Could the 19 have more cup to it?