19p vs 21p big deal ?

[calvinator]

My current setup:
1995 Wellcraft Eclipse 210SC, approx 3800# fueled & passengers.
Volvo Penta 5.8FL w/Volvo Penta SX outdrive.
14" x 21p x 3 blade aluminum prop.

Nice setup, but looking for more holeshot/acceleration. We use our boat for tubes and short acceleration runs. Found a good results review of a similar boat with a 14.25" x 19p x 4 blade Volvo Penta prop (VP partno 358722). So I started shopping for that prop. New cost is about $200.

Found a boat place going out of business. I bought a sealed box Volvo Penta partnumber 358722 - $80. Open the box and the prop is stamped Volvo Penta partnumber 358724 -- 14" x 21p x 4blade aluminum--- DOAH ! ! !

So, I'm hung up on my good prop deal, but thinking there is little difference in my two props -- both 14" x 21p, one is 3 blade other is 4 blade.

Am I really going to notice anything between a 14" x 21p x4 and 14.25" x 19p x4 so I can keep my good prop $$ deal, or should I reset here and get that 14.25" x 19p x 4 prop ?

Thanks -

 

[Silvertip]

Re: 19p vs 21p big deal ?

Results will depend on how the 21P 3 blade performed. If the engine revs at or very near the top of the manufacturers wide open throttle rpm band with what you consider an average load, then the 4-blade will likely pull off some rpm but performance may stay about the same. If the engine can't reach the upper end of the band with the 3 blade, going to a 4-blade will likely make it worse. If the engine tends to over rev with the 3 blade, the four blade would be a good choice and would very likely give you the hole shot you are after. So the answer again is -- it depends!

 

[cribber]

Re: 19p vs 21p big deal ?

You should see an improvement in hole shot if you're near WOT max rpms. Speed is a toss of the coin... I lost top a little top end speed but got terrific bow lift and about a second bump on my hole shot. You could actually see a little increase depending on the rest of your setup.

 

[Robbabob]

Re: 19p vs 21p big deal ?

You will see an improvement with the 4-blade, regardless of what your old numbers were. Sounds like you're not a speed freak needing to worry about your MAX RPM being exceeded as you prefer to get the hole-shot performance for the activities you enjoy.

That said, I am not sure if the 4-blade will give you enough of what you're looking for. I think I've read the 4-blade will behave like a 1" drop in pitch for hole-shot and you were looking at a 2" drop.

Bottom line, you have a new prop to use and test with. If you don't like it, you can sell it "like new, used 1 time" and make a proffit.

Enjoy!

 

[calvinator]

Re: 19p vs 21p big deal ?

Thanks all - I guess I'll keep the prop and test it out when Lake Erie un-freezes this spring.

I do recall the 21p 3 blade I was at 4300 RPMs which is at the top range for my motor. So the 21p 4 blade should get me there too. If not there is always eBay

 

[Robbabob]

Re: 19p vs 21p big deal ?

Thanks all - I guess I'll keep the prop and test it out when Lake Erie un-freezes this spring.

I do recall the 21p 3 blade I was at 4300 RPMs which is at the top range for my motor. So the 21p 4 blade should get me there too. If not there is always eBay

You sure your motor doesn't want to turn 4600?

Please review this sticky http://forums.iboats.com/showthread.php?t=287818 and let us know more information. If your engine wants to see 4600 max, then a more aggresive prop will suit your needs (better).

Give us the data you know about your 21P and we can give better input. If you don't know, then we'll just wait until the ice melts.

 

[v20 outrage]

Re: 19p vs 21p big deal ?

I believe that engine wants to spin 4600 rpms, so going to a 4 blade 21p is not going to allow it to get there.
If you want more bottom end [ hole shot ] you need to go down in pitch, not up.
Over propping that engine, [ to much pitch ] ....is not allowing it to reach it's factory recomended top end rpms, & will not only reduce performance, but also shorten that engines life big time.
If she wants 4600 rpms per factory recomendation, than go down in pitch until she reaches it, than you will see a big improvement in your hole shot & ability to carry a bigger load.