elaphant ear 3 blade vs 4 blade?

[rthomas]

I'm currently running a 16-16 3 blade elaphant ear and im wondering if going to a 4 blade would serve me better. the boat is the 22 in my sig and with fuel and gear/passegers weighs 4500+. with the 3 blade it planes at 20-21 tops out at 38-40@4500 rpm best econo cruise is at 3100-3300 @23-24 mph avg 2.5-2.6 mpg. my objective is better fuel economy and slower plane speed, top end isnt a concern. I dont think im doing that bad with the prop i have but i have to wonder if a 4 blade would be better?

 

[rthomas]

Re: elaphant ear 3 blade vs 4 blade?

BUMP I thought i would try again!

 

[hwsiii]

Re: elaphant ear 3 blade vs 4 blade?

R, theoretially the elephant ears prop you have normally does a very good job of lifting heavier boats like yours. But as a normal course of events if you would change to a Solas aluminum Amita 4 blade prop in a 15" pitch you will find that you will have better control at slower speeds, your planing speed will be slower and your acceleration will be better.



H

 

[dan t.]

Re: elaphant ear 3 blade vs 4 blade?

Unless you can borrow 1 to try dont spend the money,I have a Bayliner 2452and was running a 16x16 elephant ear prop, from reading these forums and fron Mercs prop selector I decided to buy a 15x16 4 blade, what a POS.Time to plane trippled, cruise speed of 20 knots went from 3600 rpm to 4000 and lost 2 knots wot. A good improvement to your current prop is to add some cup, for me it dropped cruise rpm by 100 with a noticible better hole shot.
good luck

 

[hwsiii]

Re: elaphant ear 3 blade vs 4 blade?

R, You might try reading this for a better understanding of changing props for better performance, and for the major differences between aluminum props and stainless steel.

http://forums.iboats.com/showthread.php?t=369057



H

 

[rthomas]

Re: elaphant ear 3 blade vs 4 blade?

Thanks guys, my only real complaint about the prop(s) I have now is their tendancy to vibrate a little, the good thing about the prop i have is the incredible hole shot and tractor like ability to climb out of the hole-it will get up on plane with 9 adults on board. With the lack of raking and the huge diameter could this be a killer on economy? Most of my boating is day cruising @22-27 mph. 1500+mi. last year economy is an issue for me. Thanks -Russ

 

[Silvertip]

Re: elaphant ear 3 blade vs 4 blade?

You aren't going to change economy significantly enough to justify the cost of a different prop. You are heavily loaded. Slowing the engine down merely means it lugs more getting out of the hole which then requires more throttle to overcome so you hurt economy rather than improve it. Besides, if a prop is wrong at wide open throttle it is wrong across the entire RPM band. So prop the boat so the engine reves at or near the top of its recommended rpm band and economy and performance will be the best it can be. My suggestion would be to install a fuel flow monitor so you can actually monitor fuel flow. Now you could instantly observe where best throttle setting is for maximum economy. Maximum economy may not and likely will not be at the speed you consider best cruise speed.

 

[rthomas]

Re: elaphant ear 3 blade vs 4 blade?

Im not really after an overall change in pitch- what I have now is very good, slightly under- with a fresh tune it'll rev to 4700, Id rather have that than be over pitched. Im just entertaining the possibility that a comperably pitched 4 blade would be better on fuel. I have always had a fuel flow meter on this boat (LMF400) and your right they definately help you find the sweet spot, this year I added a speed wheel so I get real time economy numbers, - I know speed wheels arent considered to be very accurate at speed but the posted mpg was done with gps