The age old 3 vs. 4 blade

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Caddy84

Recruit
Joined
Aug 14, 2011
Messages
2
I looked through the posts but can't find an answer for this.

What differences are there between an 3 and a 4 blade when only the number of blades differ? I've seen posts where other specs change at the same time like pitch and going from an Al to SS, but never just the number of blades.

I have a 1984 17' Cadorette bowrider (can hold 10 people) with a 1983 115 hp Johnson outboard. I want to use the boat for tubing, but at present the holeshot is lousy. I mean the boat looks like a dog dancing on it's hide legs and that's just with 3 people in it and not while tubing.

Thanks.

p.s. great site.
 
SparkieBoat

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: The age old 3 vs. 4 blade

read the read first post at the top of the forum. get a set of trim tabs, they will help hole shot big time. we can make prop recommendations after you post the needed info.
 
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steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: The age old 3 vs. 4 blade

Describe load and hole shot is hole shot in seconds or minutes?
Prop size max rpm and speed?
All being equal a 4 blade should deliver better hole shot,stay on plane with less throttle
better response,handle better at the dock.top speed likely will be less though there is a recent post with same size producing faster speed and higher rpm and venting sensitivity
so nothing is carved in stone.I wouldn't go for tabs until you have checked your setup.
 
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Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: The age old 3 vs. 4 blade

While it's true we could use some more info we can still talk about a few basic things. It's not unusual to find it's benifical to have 2 props, one for normal cruising / running and one for pulling water toys. Especially with older V4s. With the "water toy pulling" prop we don't worry too much about top rpm. Even if you do pull your tube at wide open you'll still be watching the tach, no big deal. The "pulling" prop will mosy likely be 2 to 4" less pitch than the "efficient" prop. Naturally we'll talk about what prop and set up is best for your "normal" prop first.
 
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Caddy84

Recruit
Joined
Aug 14, 2011
Messages
2
Re: The age old 3 vs. 4 blade

Thanks for the input everyone. It's a 3 blade aluminum and I just got the numbers off it and was told they are BMLC9356, which doesn't help much. I'm not at the boat so I need to go look at the prop myself. Once I know what the pitch is, I can see what changes need to be made. The boat is mostly being used for tubing and I'm not too concerned with top end speed. However the "2 prop" idea is a good one to have.

Thanks again and I'll keep you posted.
 
doggfather69

doggfather69

Seaman
Joined
Jul 25, 2011
Messages
52
Re: The age old 3 vs. 4 blade

I have a 18.5 foot bayliner tri hull. Its a Volvo Penta aq120b with a 270 outdrive. I recently switched from a 14x19 3 blade to a 14.5x17 4 blade. I havent pushed it much yet because of other issues but it seems to perform better thus far. This week I am going out to push it and see exactly what it can do. The theory is that going from a 3 to 4 and not changing the pitch you will gain hole shot and lose top end. I didnt want to lose top end so I went down in pitch. I will have it out all day on wednesday, I will let you know for sure!
 
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Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: The age old 3 vs. 4 blade

When we're talking about props and performance (efficiency) we have to keep in mind what package we're talking about. We have options with an outboard that we don't have with I/Os. That's why there are 3 and 4 blade props made for outboards and different ones for I/Os.
 
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