NEED HELP, New Prop, Boat not running right

[do420jc]

I picked my boat up from the dealer yesterday, 2000 21V. With the a new ACME 525 3 blade prop the dealer put on for me. Took it out this morning and at 10 mph my rpm's are maxed out. Is there something he didn't do correctly or an adjustment I can make. Got the boat back last night with the new Monstet tower and ACME prop, and got the family up at 4:30am today to ride and no go do to the prop situation. How discouraging. Any insight would be great.

[Tequilasun]

I'd be making a call to the dealer to come fix that problem right now!


Maybe they put the prop on backwards.

[dogbert]

If the prop is on backwards, then your throttle would work in the opposite direction. My guess is that they forgot the square pin that goes in the groove of the prop and the shaft. It's either missing or damaged and your prop is spinning freely. This should be easy enough to check either by inspecting it or putting the boat in gear (with the engine off) and attempting to turn the prop. If you can turn the prop by hand, then something is slipping. I'd start looking at how the prop is installed and work my way towards the V-Drive and the transmission. You might want to check your tranny fluid to make sure it's ok.

Just for reference, I have the same boat as you (Monster tower and all) and I get about 45 Mph at WOT.

[Tequilasun]

I guess I forgot to convey I was joking....


Here you go dog

You're probably right about the spline, but I have seen stranger things than a prop put on backwards!

[dogbert]

Originally posted by Tequilasun
I guess I forgot to convey I was joking....


Here you go dog

You're probably right about the spline, but I have seen stranger things than a prop put on backwards!

Thanks for telling me what the name of it is...now I don't have to refer to it as "...that square thingamajiggy in between the prop and the shaft".

[Tequilasun]

Spline might not be the right term either, my dad calls it the Shear pin.

[raythompson]

Don't call it a square "thingamajiggy" as people will surely laugh. It should proplery be called a square "doo-hickey".

And yes, my guess is that the "key pin for the prop" was not installed and the prop is spinning on the shaft.

[spharis]

Shear pin......at least that's what it's called around here and on any tractor spline.

[Lucky 275]

If it's the shear pin, you should be able to spin the prop by hand and it will slip on the shaft. Did it work with the old prop, or is this the 1st time you've had it out?

[dogbert]

Originally posted by raythompson
Don't call it a square "thingamajiggy" as people will surely laugh. It should proplery be called a square "doo-hickey".

I was fixin' to say that!

[do420jc]

Well, just got back from lake after going back to the dealer. He says that the Acme 525 is the wrong prop for my Boat. In 2000, on the 21V they had 2 different transmission's. I believe that he said one of them was 1.1 ratio and the other was what I have. He also said the 1.1 ratio is grey and mine is blue? Does this sound right? In the end he banged my old prop pretty much back to normal. Just got back from the lake and the performance with my old prop is 100 times better so I am just going to keep it and return the 3 blade back to Wakeside. All in all the dealer was super helpful.

[lee]

The blue v-drive is Synchrotech with a 1.5:1 ratio.

[Lucky 275]

All the newer Vs run the Acme 537 4 blade with the Synchrotech gear reduction. Is there a reason you went with the 3 blade?

You might also check out.
http://www.propellersonline.com/Acme.php

Substantial savings over wakeside. $355 for the 4 blade 537.

[do420jc]

I went with the 3 blade because I heard that the holeshot was awesome and with alot of ballast the pp holds very well.

[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".