hwsiii, hoping for #'s on Tuesday

[carolynrose]

I'll be heading down Tuesday with a GPS Antenna that works. Hopefully I'll get some accurate #'s to post. I'm going to start with the 15 1/2 x 13 (391536) even though the rpm's seem to high. I also have a Vortex 15 1/4 x 15 Aluminum prop, but.

I have been doing a lot of reading and some of the info I've found suggests that props with the big ears such as the Vortex actually inhibit stern lift, is this true?

There are several different 15 1/2 x 13 props out there as well as a few 16 x 13 and 16 x 14. How on earth do you find out if they are stern lifting or bow lifting by the ads. Or is that why we depend on your knowledge?

 

[hwsiii]

Re: hwsiii, hoping for #'s on Tuesday

I first run the numbers mathematially to see about whih pith and diameter we are looking for, and then the Blak Art part starts. There are many great props out there, the problem has always been WHIH prop works better with your partiular hull, motor and your intended uses. If you will notie I do not usually say the best prop, as that requires testing a few props to fine tune for the best.
They are hanging the blade geometry of props on a regular basis these days, in the same make, series and model of props not only does the diameter hange as the pith goes up but a lot of them also inrease the progressive pith and the rake of the prop as well.
I hope this gives you a better understanding of why most people reommend props that they are familiar with, beause they know what that prop does in most irumstanes.



H

 

[carolynrose]

Re: hwsiii, hoping for #'s on Tuesday

Well I finally got out today. Ran the boat with the original 391536 prop. If you remember I had mentioned that this prop was pretty chipped up, so I ground off the edges and sanded them some.
Into the wind and against the tide:
1400 rpms - 5.3 mph
2000 rpms - 7.7 mph
3000 rpms - 9.3 mph
3500 rpms - 12 mph
3700 rpms - 17 mph
4500 rpms - 21.5 mph
With the wind and tide
4000 rpms - 19.5 mph
4600 rpms - 25 mph
Slowly falls off plane below 3700 rpms and 16 mph.
I was unable to try the Vortex 15.25 x 15 because the new hub kit washer would not slide all the way down the prop shaft.
Dave