NEED HELP, New Prop, Boat not running right

[Lucky 275]

Probably unhooked the trailer from the truck instead of the boat

[race fan]

funny

[do420jc]

Originally posted by spharis
That still doesnt make sense.....3 blade causing you to go that slow.....I could see poor hole shot or something due to less surface area and a higher pitch, or leading edge; but to barely move. Your propshaft still turns 1 rev per 1.5 engine at that engine RPM, and usually a 3 blade means more speed and less on the low side. Sounds like it was installed wrong.

Acme-537 13.5 / 16 / LH / 4 / 1-1/8"
Acme-525 13 / 11.5 / LH / 3 / 1-1/8"

on second thought that is a retty drastic change on the pitch......4.5 inches, and less surface area.....

Not taking into account slippage....for every 1 turn of the prop, you should go foward 11.5 inches vs 16 inches on the stocker. You also went down in diameter and blades, so you probably lost about 25% surface fast. Rough estimate is that that netted about 5% decrease in overall speed + 30% decrease in pitch vs. distance, so even with no slippage, you would be going about 35% slower at useable RPM range, or old 50MPH = new 32.5MPH

Theoretical mph is calculated by multiplying propeller pitch and propeller rpm and dividing by 1056 (found that online).
So MPH w/4 blade = (16*(5000*.66))/1056
or 50MPH
MPH w/3 blade = (11.5*(5000*.66))/1056
or 36MPH

So either you were getting hella slippage, or the prop was installed wrong....either way......it would be alot slower.
I think the rule is to go from a 4 to a 3 @ about the same performance:
Maintain diameter, and increase the pitch 1".

WOW. I definitly didn't put that much thought into it. Not even close. The first thing I thought of was bring it back to the dealer. 2nd this sucks. 3rd thing whats for lunch.? I am going to just stick with the 4 blade I have at this point.

[do420jc]

Originally posted by Lucky 275
Probably unhooked the trailer from the truck instead of the boat

You know your right, that could have been bogging me down.

[dogbert]

Originally posted by do420jc
You know your right, that could have been bogging me down.

Sounds like your dealer screwed up and didn't want to admit it

[Moki]

Originally posted by spharis
That still doesnt make sense.....3 blade causing you to go that slow.....I could see poor hole shot or something due to less surface area and a higher pitch, or leading edge; but to barely move. Your propshaft still turns 1 rev per 1.5 engine at that engine RPM, and usually a 3 blade means more speed and less on the low side. Sounds like it was installed wrong.

Acme-537 13.5 / 16 / LH / 4 / 1-1/8"
Acme-525 13 / 11.5 / LH / 3 / 1-1/8"

on second thought that is a retty drastic change on the pitch......4.5 inches, and less surface area.....

Not taking into account slippage....for every 1 turn of the prop, you should go foward 11.5 inches vs 16 inches on the stocker. You also went down in diameter and blades, so you probably lost about 25% surface fast. Rough estimate is that that netted about 5% decrease in overall speed + 30% decrease in pitch vs. distance, so even with no slippage, you would be going about 35% slower at useable RPM range, or old 50MPH = new 32.5MPH

Theoretical mph is calculated by multiplying propeller pitch and propeller rpm and dividing by 1056 (found that online).
So MPH w/4 blade = (16*(5000*.66))/1056
or 50MPH
MPH w/3 blade = (11.5*(5000*.66))/1056
or 36MPH

So either you were getting hella slippage, or the prop was installed wrong....either way......it would be alot slower.
I think the rule is to go from a 4 to a 3 @ about the same performance:
Maintain diameter, and increase the pitch 1".

Hypothetically speaking, without prevarication or verboseness, I would take the coefficient of stored energy of the potential mass of the propeller divided by the ambient temperature to the power of 3, squared by the average temperature of Hawaii to determine the hyperbole of the angle of incidence. This, of course, to be used in accordance with Bertrand’s paradox. Unless, you determine the harmonic ratio of the propeller do be in conflict with Wittenbauer's Parallelogram...... or you have it on backwards

Seriously, very impressive research and analysis spharis!

[spharis]

Originally posted by Moki
Wittenbauer's Parallelogram......

Thats the 3 sided one right?

[do420jc]

Spharis, did you end up getting a new tower yet for boat?

[spharis]

I think I am going to do the interior first......I am working on my gelcoat currently.

Send me yours.....

[TigeDuner]

After reading all this, I still have a question that I need some help on. I am looking at a 2005 24V to purchase and it has a three blade prop that came with the boat when purchased new. My 2000 2300V has a four blade prop. Will the three blade do as well on the 2005 as my 2000 or did someone shave some dollars on the purchase of the 2005? I do not know any of the particulars of the 2005 prop only that the 2005 has the 340 hp motor. Thanks

[spharis]

What is the prop measurements....You can run a 3 blade on it as well as a 4 blade if the proper size was chosen.

[lee]

Originally posted by TigeDuner
I am looking at a 2005 24V to purchase and it has a three blade prop that came with the boat when purchased new.

I have not heard of this before.

[dogbert]

Originally posted by lee
I have not heard of this before.

My dealer started putting those larger Acme 3 blades on all their new boats. I recently moved my boat from a 4 blade OJ to a 3 blade Acme. It makes a big difference on the holeshot. Check out this thread.

[TigeDuner]

Your old post was helpful. Sounds like I don't need to be concerned about the three blade at all. Thanks...

[spharis]

If you can get the size of the prop, and compare it against the stock one, you can work out what kind of top end you would possibly gain. As far as hole shot, there is no formula for that one.