4 to 5 blade conversion

masher44 · 03-02-2007, 11:46 AM

What would a size/pitch guesstimate be for converting a single 6 drive 32 Activator that runs great with a 17" x 33 4 blade to a 5 blade? Thanks Jim

throttleup · 03-02-2007, 12:53 PM

Hey Masher44,

You will reduce one inch of pitch to compensate for the drag, of the additional blade.

Julie

masher44 · 03-02-2007, 03:06 PM

I ran a 16.5 X 31 at 6700 rpms and want to get the rpms down to about 5900 and increase top speed. Boat pulls to 90 like a monster now but want to get a bit more on the top. I was thinking a 17 x 33/34 or so to get there.. will that be enough increase with the extra diameter and pitch? Also tried a 17.5 x 28 and the boat likes diameter but not sure about the 17.5 with a 33 pitch.Thanks, Jim

throttleup · 03-02-2007, 03:15 PM

What rpm does the motor make peak HP and TQ? Those numbers will determine the WOT rpm. Over propping a boat like your can lead to many problems.

Do you know the gear ratio?

masher44 · 03-02-2007, 03:53 PM

Quote:

Originally Posted by throttleup

What rpm does the motor make peak HP and TQ? Those numbers will determine the WOT rpm. Over propping a boat like your can lead to many problems.

Do you know the gear ratio?

It is a 32 Activator single with a wet sump 6 making about 930hp/900trq at about 6000 rpms. That boat ran 6700 with the 16.5 x 31.
1.5 on the ratio.

throttleup · 03-02-2007, 06:03 PM

At what RPM is the peak torque produced? Just want to make sure you stay away from that RPM. If you need to decrease 800 RPM the diameter increase with the pitch increase will do the trick. I would think that no larger than 17' diameter with that tall of a pitch. I would think 32-33P range.

Julie

masher44 · 03-03-2007, 04:05 AM

Quote:

Originally Posted by throttleup

At what RPM is the peak torque produced? Just want to make sure you stay away from that RPM. If you need to decrease 800 RPM the diameter increase with the pitch increase will do the trick. I would think that no larger than 17' diameter with that tall of a pitch. I would think 32-33P range.

Julie

Thanx! Just what I was thinking... I will have to find out from JC when peak torque is in mine.. I think a 17 with 32-33 is the ticket... got a cheap one for sale?

bbladesprops · 03-03-2007, 03:38 PM

Going from 4 to 5 blade propellers can involve diameter adjustments. In fact, we prefere to do this to maintain speeds. I don't like to give away too many secrets on this site. People tend to copy us word for word........HEHE.

It's a 2 sided sword.

Call us anytime and we can discuss your application.