3 Blade or 4 blade prop?

Joined
May 20, 2020
Messages
5
I have a 90 HP Force on a 17' combo bass boat, I have always used a 3 blade 17 pitch prop. Anyone have a pro or con on going to a 4 blade, and should I reduce the pitch to 15 on the 4 blade? Looking for the described extra lift and fuel economy that the 4 blade is supposed to provide.
Be safe, thanks
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
11,795
Min-Max wot rpm factory stated ?
Current Load ? Number of Passengers ?
Max achieved wot rpm with 3 blade 17 pitch prop ?

Happy Boating
 

JimS123

Admiral
Joined
Jul 27, 2007
Messages
6,812
If you think you need stern lift, there are better ways to achieve it. If you would be disappointed when you lost top speed, a 4-blade isn't the way to go. The reported fuel savings are real, but unless you boat 7 days a week you probably won't take it to the bank.

If you want to increase top speed, mid range performance AND improve economy, a state-of-the-art SS Mercury Marine prop (like an Enertia) is what you want.

Yes, if you go from a 3 to a 4, the pitch will need to be reduced, but how much will require GPS and RPM data to dial it right in.
 

QBhoy

Vice Admiral
Joined
Mar 10, 2016
Messages
5,377
For me…it depends what the 17” 3 blade you have now is and how it goes. The thought around a 4 blade being better on fuel than a 3 blade…is a tough one for me to swallow. Be a brave man that would argue against sheer physics and it’s laws telling us that less blades always means greater efficiency. Perhaps the confusion comes from a 4 blade occasionaly offering slower planing speeds than a 3 blade. But this doesn’t always mean using less fuel. Lots of variables to consider in play here.
gpimg back to where I started. The notion of going down in pitch from 3 to 4 blade, heavily depends on what 3 blade you have. An example of why you wouldn’t go down in pitch, I can testify to, is if you have a big bladed stainless 3 blade and went down 2” in pitch to a ally 4 blade…you 100% for certain aren’t going to see anything but an increase in rpm everywhere.
As for the notion of more loft from a 4 blade…again it depends on what 3 blade you have now. And what 4 blade you go to. Will going from a cheap solas 3 blade ally prop to a stainless 4 blade bravo or Rev 4 see more lift…certainly…but will going from a tempest or enertia to a solas 4 blade see more lift…certainly not.
Finally…added to all this, the motor you have had only a limited bandwidth of props available in terms of this. It’s likely you’re dealing with ally props perhaps. My opinion for what it’s worth…in your situation, I’d doubt you will get too much better efficiency and lift from any normal 4 blade, over the good old go to and dependable 3 blade laser 2.
 

poconojoe

Lieutenant Commander
Joined
Sep 10, 2010
Messages
1,611
I have a 90 HP Force on a 17' combo bass boat, I have always used a 3 blade 17 pitch prop. Anyone have a pro or con on going to a 4 blade, and should I reduce the pitch to 15 on the 4 blade? Looking for the described extra lift and fuel economy that the 4 blade is supposed to provide.
Be safe, thanks
Probably not a good idea to use your email as your handle....just saying....
 

Texasmark

Supreme Mariner
Joined
Dec 20, 2005
Messages
14,005
I was running a 3 blade 20P early edition Laser II which would run 48 on calm water, summer heat. As you are talking here, I like to run around 3000 RPM and 25 mph most of the time so I bought a Solace 4 blade 19P. I lost 3 mph of top end (and some RPM) which I don't miss (because I know I can get it back if I swap props back). 2 things at work here....the extra blade efficiency reduction and the stern lifting characteristic which reduces the bow lift necessary to get the hull out of the water, reducing drag to make the top end MPH.

The Laser is ported making for hole shot assistance and the Solace isn't but the 4th blade and prop design made a much more robust shot and easy cruising where I like it. The 4th blade and design give me much more control on maintaining speed and "posture" running at the lower speeds.

Solace has a tutorial and address the stern lifting characteristics of their 4 blade and the bow lifting characteristics of the 3 blade when top end is the main objective. Blade design is somewhat different besides the extra paddle.

PS: After I closed this I happened to look at my post count and 14,000 is a lot of slinging BS around....LMAO
 
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lprizman

Chief Petty Officer
Joined
Jul 9, 2009
Messages
425
Ken from Prop Gods a member here???
He's on 2 other sites I'm on.....he'd know....
However that year and long-ago 4 blades were not in I believe at that time on that size and style set up
 
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