3 blade or 4

[gostephen]

ive herd that there can be a significant performance difference between a 3 blade and a 4 blade. what are these differences?

i have also herd that you should drop 1in of pitch when changing from a 3 blade to a 4

 

[hwsiii]

Re: 3 blade or 4

Steve, if you could tell us what problem you are trying to cure, we could give you a more specific answer to that problem, as 4 blade props are not a panacea for all problems.
The reason that most people say to drop one inch of pitch for a 4 blade is because they usually have more blade surface area, so they won't turn as many RPM as a 3 blade, but that is not always true.


H

 

[wellsc1]

Re: 3 blade or 4

Steve, to me, props were black magic, voo-doo, or just plain mysterious. However, the wonderful witch doctors and magicians worked miracles in this forum. This thread could take you on a wonderful journey into prop science. Get ready to learn about cup, rake, half-clever, slip, pitch, efficiency, and a myriad of magic words that will wow you. I think hwsii is one of them.

 

[captmello]

Re: 3 blade or 4

I've been looking into a four blade as well. According to info on the Iboats prop info, they say a two inch drop in pitch from 3 to 4 blade.

They also claim lower rpm planing speed and better hole shot. I wonder if these are noticable or just slight improvements.

 

[gostephen]

Re: 3 blade or 4

im not having any problams. ive herd that 4 blades give better hole shot, better controall on conering. and better top end.

i am using a 17p aluminum 3 blade
rec wot 4200-4600
current 4300 (i run at an elevation of 7000ft)
1989 celebrity 181 bowrider 18ft
4.3l merc alpha1 175hp

im looking to upgrade my prop but stainless is out of my price range
primary use is tubing and skiing, cursing around

 

[Dhadley]

Re: 3 blade or 4

There are many styles of 4 blade props. Most are aimed at the outboard market. When someone talks about dropping pitch when going from a 3 to a 4 they probably mean they are not willing to change the set up on the outboard to take advantage of the technology. With a sterndrive you don't have the luxury to easily change the drive height or X dimension. There are 4 blade props designed specifically for sterndrives. Generally speaking, there are 4 blade props designed for running close to the surface and some are designed to run deeper. We'll assume your outdrive is positioned so the AV plate is even with the keel. If so, then the higher technology 4 blade props may not do you much good.

With the right 4 blade prop I think you'll be very happy. Especially pulling water toys.

 

[junior1113]

Re: 3 blade or 4

better hole shot
better reverse
slower on plane speeds
better mid -range fuel economy
better cornering
better top speed
better stern lift
better acceleration
better towing toys
better handling in rough condition
better with heavier loads
these are the differences i noticed after 3 to 4 blade
cant think of one thing the 3 did better than the 4.
if i was in your shoes 15p ss 4blade.turbo has a great inboard 4 blade prop
honestly dont know why any one has a 3 blade ill never go back