Nibral vs Bronze Fuel Economy

[Marshall Mahoney]

I have 300 HP Cummins. With 20 x 23 4 blade Nibral Hytorq props, I was getting approx 1.5 mpg. I lost a prop (sheared shaft) and replaced both props with 20x23 bronze (unknown model) that I got a deal on. Now I am getting noticeably less mpg -- I am guessing 1.2 mpg based off of 2 trips. That is a 20% reduction in fuel economy. For the sake of argument, with all other variables being the same, is it possible that bronze would be 20% less efficient? I think not...

[Carl]

For the sake of argument, with all other variables being the same, is it possible that bronze would be 20% less efficient? I think not...

"with all other variables being the same"

That is where you are having an issue with the comparison of Nibral to Bronze. All other things are not equal, you are comparing bronze props to hytorq. They are two very different wheels that also happen to be made from two different materials.

Nibral being stronger "can" be made thinner which creates less friction in the water which is more efficient, but as you said...not 20%.

I said "can" be made thinner...but being stronger the manufacturer can also change the style, add more surface area while still being able to handle the power of the motor. So you're comparing a hytorq...which I believe only makes nibral to another make and style wheel of the same size. The Bronze to Nibral comparison is only a small part of the equation.

[Marshall Mahoney]

I agree; a multi-variable equation with multi unknowns. I should have paid attention in that class. I'm just trying to get a reality check on the bronze props, of a different design, but with the same diameter and pitch, being 20% less efficient. That way I can decide if I can justify forking out $1600 on a replacement hytorq or start troubleshooting other issues. Boat is out of the water now (attempting a paint job). I will see if I can get a model number off of the props and send the info to Michigan Wheel for their opinion.

[Carl]

With 300hp Cummins on a 31, you will want Nibral wheels. Which ones I'd leave up to those that really know.
Michigan makes lots of different style wheels, but nobody else's. What I'm saying, walking into a Dodge dealership, expect them to recommend a Dodge.

Acme is another jump up in price, but you're getting near-perfect wheels.



I have the 210's...not enough power to justify the cost of going Nibral in my opinion.

I kinda kept the Bronze vs Nibral question / single variable, but when I think Nibral I think high-performance props, not just the material being used....if that makes any sense.

[bob lico]

then there is that one guy who goes with a Ron Ellis Nibral propeller with its own unique design.

[Craig Mac]

I have not compared bronze & Nibral side by side, but was told by a knowable person that most production is using the same thickness for both---

Maybe some of the higher-tier brands refine the process to take advantage of the superior properties.

[Carl]

I have not compared bronze & Nibral side by side, but was told by a knowable person that most production is using the same thickness for both---

Maybe some of the higher-tier brands refine the process to take advantage of the superior properties.

Same wheel in nibral vs bronze, the advantage of nibral being stronger is the reduction of blade flex under load. Lower power motors like my 210's see little to no advantage of nibral, add some more hp and that changes. Go nibral or the blades would need to be beefed up to handle the load which kinda goes back to the blades "can" be thinner thing.
Variables...lots of em with props.

[Carl]

then there is that one guy who goes with a Ron Ellis Nibral propeller with its own unique design.

Then there is that one guy...

Lots of blade area on those Ellis wheels. I remember trying my dads Ellis wheels on my boat with the 440's. Same size and pitch as what I was running, but I could not get boat on plane. Too much wheel.

[Marshall Mahoney]

I sent Michigan the question last Tuesday -- have not heard back. I must have dumbfounded them! Thanks guys for your feedback...

[Carl]

If you think waiting a week for a response is long...wait till you hear the lead times.

[bob lico]

carl that's the key words"to much wheel" you have three blades with the same metal in the water as a four blade. the cummins have gobs of torque .the object of the performance game is to utilize this.each engine putting out almost two and one half times the torque of those 440's.

[Carl]

Bob-
Cummins is a different animal for certain. I don't have that one-on-one comparison to play with anymore as he went high revving Steyr motors where I went slow revving Cummins. The plus for him was the conversion was a bolt up...motors were the same size and lighter than the 440's, no need to change shafts, logs, exhaust etc. He just had to repitch the wheels, clean tank and done. That another story...

The Ellis wheels were back in the day when Dad and I both were running 440's. His boat is heavier, but a Flat bottomed 28 Hatteras and me in my 31. With the Ellis wheels he was able to get up and go, I could not get on plane. Same when we played with rake...my take has been getting these 31's out of the hole takes lots of power.
Yes, Ellis puts lots of blade in the water, it was just too much wheel for my setup.

[bob lico]

agreed 100% if you have Cat,cummins utilize the torque to the maximum. my brain is coming apart at the seams i just came back from buying coloring books and color pencils for my wife , believe me i rather handle a sewerage on a 31 Bertram any time

[Carl]

Bob- it would be great if life was fair...



Yes, dealing with raw sewerage would be easier to deal with than the present hand your wife and you have been dealt. I've always looked up to your knowledge, abilities and willingness to share them...being there like you are for your wife has truly risen that bar higher. Thank you for being an inspiration.

[Rawleigh]

You are a good man Bob! I cannot imagine your anguish! We are all praying for you and your wife. The only good news is that you will go to your reward with a clean conscience knowing that you did everything humanly possible for her. Keep up the good work. Your friend, Rawleigh.

[DanielM]

Bob,

I tried to send you a PM a couple days ago but it never left my outbox. I must be doing something wrong.

Just wanted to let you know your wife and you are in my thoughts and prayers.