Prop help

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Jnitti1014
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Prop help

Post by Jnitti1014 » Wed Feb 14, 2018 10:45 pm

Can someone school me on propellers? I need to buy a new one for my 2002 26x with a Honda bf50. I want fuel efficiency over low end grunt. Also trying to decide between aluminum and stainless steel. My old aluminum one got bent backing into my berth.

C Buchs
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Re: Prop help

Post by C Buchs » Thu Feb 15, 2018 12:50 pm

I've got the same boat and motor. This 4 blade has been in my Amazon cart for a while: https://www.amazon.com/gp/product/B00AJ ... =pda0fc-20 I believe that Tomfoolery recommended this one for pulling a tube. Probably not what you're looking for, but it might be helpful for someone else. I just had to install the extra 3 blade that came with my boat after spinning the rubber in my old one. I'm not positive which 3 blade to get.

Jeff

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Tomfoolery
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Re: Prop help

Post by Tomfoolery » Thu Feb 15, 2018 1:41 pm

The original Honda prop was also made by Solas (but with Honda stamped on it), but it was the 11-3/4" dia x 10" pitch x 3-blade with the Grim Reaper sickle blades.

Image

The 3-blade seems a bit more efficient than the 4-blade (11.8" x 9" pitch), and gives a higher top end, but the 4-blade seems to have a better bite on the water when towing and docking. BUT - the 4-blade makes an annoying howl when running between 2000 and 3000 rpm, and I'm not the only one with that engine/prop combo that's experienced it. Since I do most of my motoring in that slow range, I've switched back to the 3-blade, and keep the 4-blade in reserve, and in case my youngest visits and wants to wakeboard.

I stick with aluminium because it's cheap, and I'd rather the prop take a beating than the OB. I don't care about maximum high-speed performance, which is where stainless is supposed to be better, as it's much stiffer (about three times as stiff as aluminium, all other things being equal).

For low-power, fuel efficient operation, you'll probably get greater mpg using an even steeper pitch at low engine speeds. Like for extended cruising at trawler speeds. Some folks here have done that, though not necessarily with the Honda, with no intention of running wide open. Maybe someone with first-hand knowledge of that could fill you in. I might even give it a try some day, just to see how it does, since I almost never open it up any more.

And do be aware that props from different manufacturers with the same dia. and pitch may perform differently. There are a lot more variables in prop design than just diameter and pitch.

whgoffrn
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Re: Prop help

Post by whgoffrn » Thu Feb 15, 2018 8:39 pm

My vote is for a cheap aluminum one ....they bend when you hit stuff ....stainless won't bend as easily thus tearing up lower unit

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opie
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Re: Prop help

Post by opie » Fri Feb 16, 2018 4:25 pm

My vote is for 3 blade, aluminum. Tomfoolery has spot-on advice. I decided to try a 4 blade prop several years ago and I also had the 4-blade whine so bad at slow speeds that I ditched it and went back to 3 blade. (There are some old posts about why this whine occurs....)

Needless to say, for fuel efficiency, slow down. My record is 39 miles on 6 gallons.

Jnitti1014
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Re: Prop help

Post by Jnitti1014 » Fri Feb 16, 2018 11:19 pm

So what would be the dimensions of pitch and size for a three blade propeller for a Honda bf50 for fuel efficiency over speed?

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mac n cheese
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Re: Prop help

Post by mac n cheese » Sat Feb 17, 2018 11:15 am

Jnitti1014 wrote:So what would be the dimensions of pitch and size for a three blade propeller for a Honda bf50 for fuel efficiency over speed?
Following from my notes. I hung a new BF50D on my 26X last summer which came with a Honda prop 3 blade 58130-ZZ5-000ZA (11 1/4" X 13") From what I had gathered
the 13" pitch is waaaay high for the Mac application. That prop sits in a box as a spare. I then purchased a 4 blade 58134-ZV5-009AH (11 7/8" X 9") . It's quiet
at the low end when maneuvering and docking and seems good for that. It also has some grunt when accelerating as Tomfoolery has mentioned if your pulling
something. It's impressive to see this barge lurch out of the water with that 4 blade.

Now that Tomfoolery has mentioned it that 4 blade does have a bit of a loud whine at the top end. For now though that's my current prop as I'm not really a W.O.T. guy.

To answer your question and further from my notes the most suitable 3 blade on the Mac with a lower pitch is 58130-ZZ5-630ZA (11 3/4" X 10") This prop would be my next purchase
to make any comparisons. So I would assume this 3 blade is quieter at the top end and more efficient overall with better mileage.

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Tomfoolery
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Re: Prop help

Post by Tomfoolery » Sat Feb 17, 2018 11:40 am

Jnitti1014 wrote:So what would be the dimensions of pitch and size for a three blade propeller for a Honda bf50 for fuel efficiency over speed?
The answer probably depends on what you mean by fuel efficiency. If you want to go at hull speed or less, then a 15 or 20 hp OB would be best, propped to top out at engine design speed (somewhere in the 5000-6000 rpm range), I would guess.

Keeping the BF50, but running at or below hull speed (around 3000 rpm for my boat, I believe), I would guess that an aggressive prop would be best. The engine is lightly loaded for that engine speed, since it takes very little hp to move a boat at less than hull speed. Keeping the engine speed down a bit may keep the GPH down, too. I think someone here did some research on that a while back (mastreb, I think), and provided tables or curves even, though I don't even remember what engine he used.

A prop that stops the engine from exceeding the 6000 rpm design maximum, which is what the 11-3/4 x 10" 3-blade prop in the pic above does, is what most most people use. Gives max boat speed at or near max engine speed.

Running faster than hull speed, but not up on plane, is the least fuel efficient way to fly, as all you're doing is plowing a giant wake with the bow up high. Like mid-sized go-fast boats running at half speed - they become wake-making machines that suck maximum gallons per hour, rather than the reverse.

But I can't tell you what to use, as I've only used the two in the pic above, and neither were sized for max efficiency at or below hull speed. If that's what you're trying to do.

Jnitti1014
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Re: Prop help

Post by Jnitti1014 » Sat Feb 17, 2018 11:24 pm

Tomfoolery wrote:
Jnitti1014 wrote:So what would be the dimensions of pitch and size for a three blade propeller for a Honda bf50 for fuel efficiency over speed?
The answer probably depends on what you mean by fuel efficiency. If you want to go at hull speed or less, then a 15 or 20 hp OB would be best, propped to top out at engine design speed (somewhere in the <a href="tel:5000-6000">5000-6000</a> rpm range), I would guess.

Keeping the BF50, but running at or below hull speed (around 3000 rpm for my boat, I believe), I would guess that an aggressive prop would be best. The engine is lightly loaded for that engine speed, since it takes very little hp to move a boat at less than hull speed. Keeping the engine speed down a bit may keep the GPH down, too. I think someone here did some research on that a while back (mastreb, I think), and provided tables or curves even, though I don't even remember what engine he used.

A prop that stops the engine from exceeding the 6000 rpm design maximum, which is what the 11-3/4 x 10" 3-blade prop in the pic above does, is what most most people use. Gives max boat speed at or near max engine speed.

Running faster than hull speed, but not up on plane, is the least fuel efficient way to fly, as all you're doing is plowing a giant wake with the bow up high. Like mid-sized go-fast boats running at half speed - they become wake-making machines that suck maximum gallons per hour, rather than the reverse.

But I can't tell you what to use, as I've only used the two in the pic above, and neither were sized for max efficiency at or below hull speed. If that's what you're trying to do.
Tom,

Thanks. I will use 11-3/4 x 10" 3-blade as my measurements and go from there. Yes I am looking for best gph at or below hull speed

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