Prop selection

[gordiegarland]

Currently I have a 90 optimax on 1650 fish hawk WT.
I am using a 13x19p 3 blade prop and only getting to 5200rpms, little sluggish out of the hole. Motor is operating perfectly
Specs say I should be getting up to 5700rpms
Should I go to a 13x17p ?
Would it be the same diameter and pitch for a 4 blade?

 

[alldodge]

13x17p will get you rpm up closer to 5700, but if you go to 4 blade you will need to probably go to a 15p

 

[gordiegarland]

From a 19p to a 17p, what would be the approximate increase in rooms?
4 blade would have to drop 2 pitch again to make up the rpm difference?
will I have increased rims at idle?

 

[jimmbo]

The specs say 5000 - 5750 rpms
Don't get bent out of shape if the 17" prop ends up with a dia of 13 1/4. the rpms will jump about 400 rpm and your top speed will be very close to what you are doing now, might even go up 1/4 - 1/2 mph
Going to a 4 blade will kill your top speed, unless there is a decrease in dia and an increase in pitch

 

[Sea Rider]

There's a night/day boating difference going 2 less in pitch while maintaining same 3 blade prop model, why it is that near all want to go straight to 4 blade props when haven't tested 3 blade ones with less pitch which is the way to go.

Happy Boating