3-4 blade

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JBooth

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Oct 27, 2011
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Baton Rouge, LA
How big of difference in speed and planing speed does going from a 3 to 4 blade prop make? Should the pitch stay the same or go down? Is it worth spending more on?
Thanks in advance
 
The biggest difference going from 3 blade to a 4 blade prop will be the "hole shot" or grip the prop can get in the water. Sometimes a 4 blade prop can makes all the difference for getting on plane faster. Each boat/motor is different so it's hard to say how much faster.

Assuming your 3 blade prop is the correct pitch for your engine, and you want to switch to a 4 blade, you'll probably need to either reduce the prop diameter and/or reduce the pitch. If you keep the same diamter and pitch, you will most likely not be able to reach your optimum engine RPMs and you'll probably go slower and the baot will feel sluggish.

If you want to go faster (top speed), you'll need to increase your pitch (not the number of blades), if your motor can handle it. Too much pitch, and again, your engine will not reach optimum RPMs and you'll probably go slower. Too small of a diamter and the prop will slip (cavitate) in the water and you will go slower.

Prop selection can take a lot of trial and error to dial in the perfect one. You'll probably want to find someone with the same baot/motor and see what they are running and how the boat performs.
 
I have a 25hp...mariner. I switched to a four bladed prop and definately got on plane quicker and it also had better low speed performance and responce......the flip side is I lost a little bit on my top speed but I think it was worth it
 
is it aluminum or stainless , pitch can be added or taken away to get what you need if its stainless. it is possible to get 1 1/2 inches or better in pitch up or down. don't have that luxury with aluminum
 
Just went through this. 25 Yamaha 4 stroke...came with a 9 7/8 x 10.5 3 blade aluminum prop. Max RPM 6300 (on the limiter). Decided to try a 4 blade 11" prop. I love it. But I lost quite a bit of RPM. Top speed went from 26-27 to 28-29 depending on the wind, etc, but RPM is down to 5600-5700. I have more stern lift-had to move the trim pin out one hole (all the way out now). It's on plane @ 3400-3600 with the 4 blade. With the 3 blade it was on plane at around 4000. Stays on plane easily at very low speed. Runs in shallower water when on plane due to more stern lift. Smoother running than the 3 blade. MUCH more responsive at low speeds than the 3 blade was. Reverse also works better. 4 blade 10.25x12" Solas Aluminum. Kind of wish I'd have went with a 10" pitch instead of 11" but it's what I have and it works well.
 

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