3 Blade vs 4 Blade

[Barry T]

I have a 26ft Pacemaker with a 318 cu engine, the prop that came with the boat is a 13X10 RH 3 blade with a 1 inch shaft. The question I have - Is there an advantage to changing the prop from 3 blade to 4 - if so what is it performance or economy? I`m always looking for ways to save on fuel and I am wide open to suggestions - most boats, like mine, in my area have 14 or 15 inch props with various pitches - anyone out there have any suggestions ?

 

[steelespike]

Re: 3 Blade vs 4 Blade

Speaking generically a 4 blade will help the boat plane easier and stay on plane with less power.Not sure how effective on a straight drive.
Generally prop diameter simply follows design and will vary with the pitch.
Usually a heavy boat will use a larger diameter prop.A 13 sounds small to me.

 

[Barry T]

Re: 3 Blade vs 4 Blade

Thanks for the insight, I don`t usually keep the boat on plane for very long as half of the fun is getting there - I was looking at a different prop for economical reasons. I there any way to tell what prop would be best for my boat without buying 5 and trying each one ? Please advise

 

[trendsetter240]

Re: 3 Blade vs 4 Blade

I there any way to tell what prop would be best for my boat without buying 5 and trying each one ? Please advise

You bet. Post back with the info below to get the best estimate on prop selection.

ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless and as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP (gear ratio as well)
6) Boat make model, year, length and weight

 

[steelespike]

Re: 3 Blade vs 4 Blade

Thanks for the insight, I don`t usually keep the boat on plane for very long as half of the fun is getting there - I was looking at a different prop for economical reasons. I there any way to tell what prop would be best for my boat without buying 5 and trying each one ? Please advise

Prop selection is keyed to your motors designed rpm range.The motor needs to be able to operate within that range.gph (gallons per hour) is roughly 10% of the hp. at wot(wide
open throttle) thus a 250 hp will use about 25 gph at wot.Of course less at reduced speed.
The idea is to get the most speed per rpm.
Sounds like you like to putt around Not the most practical speed when wanting to get from here to there.But can produce the best mpg.A couple of hundred rpm can be a big
difference in mpg.A flow meter really helps figure the best operating range; but needs
to be figured with the speed attained.