proper prop

[peldrid]

I have a 20' SFX with a 70 yamaha. The dealer installed a 135/8 x 13 aluminum prop. The boat on hits 21mph at 5200rpms wot. Specs on engine say 6300rpms. Does anyone have any ideas on props. Thanks 

 

[kaydano]

11.

What's the low end of the recommended RPM range?

 

[peldrid]

I think 5300rmps. I looked at performance charts on yamahas web site and the rpm range was 5800 to 6200rpms. 

 

[kaydano]

An 11 may not get you to 5800...