4 & 5 blade prop RPM's vs. a 3 blade

[FULL-THROTTLE]

It is my understanding that when going from a 3 blade prop to a 4 I should drop down in pitch to maintain top end rpm's, does this also go for a change from a 4 balde to a 5 blade?

I am presently running a 3 blade 14 1/2 diameter 19 pitch on a 2900 lb boat (empty).

Thanks

 

[Gimme Fuel]

Yes the same holds true anytime you add a blade. What are your current rpm WOT and engine model?

A merc high 5 is supposed to be a great prop for pulling skiers. You will notice a huge difference going from a 3 to 4 blade prop.

 

[FULL-THROTTLE]

Present setup

I have a Merc 260HP all stock, WOT with 4 people is 4800 with the 3 bladed 14 1/2 x 19

 

[Budman]

Depends on the prop.
The 3 blade 25p is the fastest for my boat but I have to go up to a 26 p 4 blade which I currently run.
A 24p 4 blade hits my rev limiter all the time and only good for skiing.

 

[Budman]

I have a Merc 260HP all stock, WOT with 4 people is 4800 with the 3 bladed 14 1/2 x 19

I saw your other thread looking for a prop.
I assume you're running an aluminum prop since you're looking for a sst?
If you find a sst, you may want to try it first before buying other props. The sst will not flex as much and have thinner blades than the aluminum and might work better for you.

 

[Wrenchmate]

I have a Merc 260HP all stock, WOT with 4 people is 4800 with the 3 bladed 14 1/2 x 19

My last boat was a 23 foot Fourwinns with a 350 and I ran the same prop
as yours except it was the sst and it worked great for me.
If I remember correctly 4800 was the top of the rpm range and thats
where you want to be. I also tried a 21p sst hopeing to gain some speed
and the rpms only dropped to 4600, but lost some on the hole shot and
gained 2mph with the loss in rpm. It wasnt worth it to me so I put the
19 back on. Anyway I agree with Budman and try a sst with your same
dimensions and see if that works any better.

 

[boatman4021]

Not all combo's react the same, but when going from a 3 blade like a Tempest to a 4 blade Trophy, the 4 blade in the same pitch will turn more rpm's. I ran a 27" Tempest+ and then a 28" Trophy+ and the 28 ran more rpm's and more mph. But the Trophy is a small hub design. I don't think a large hub 4 will turn as high as a 3.

 

[SunTime]

Not always.
A large prop diameter such as a Tempest Plus 3 bld vs a High Five small diameter prop can actually turn lower RPM's in the same pitch.

 

[Dave S]

Not all combo's react the same, but when going from a 3 blade like a Tempest to a 4 blade Trophy, the 4 blade in the same pitch will turn more rpm's. I ran a 27" Tempest+ and then a 28" Trophy+ and the 28 ran more rpm's and more mph. But the Trophy is a small hub design. I don't think a large hub 4 will turn as high as a 3.

On my BAJA 186 with 225 PM it runs 65-6600 rpm with a big hub Trophy 14" 4 blade, 3 blade Tempest 14 5/8" same rpm and speed. Tempest tends to chine walk a bit easier and has a bit more torque steer.
You just never know till you try.
BTW running a High Five needed to go to a 25 to get close to the same as the above props.

Dave

 

[mh2508]

props

I just yesterday took my 24 Raker II that I turned down to a 23 pitch off that works well on my boat and ran a 25 high five to try it. I was very good but I was able to over rev it if I really got after it.