two 21p props. act totally different

ric · **Posted:** Sun Aug 11, 2013 12:51 pm

The 21p 3 blade alum that came on the boat works pretty good. Gets on plane nice. But... Its dented and stuff. Unknown brand. My boat came with an Apollo 3 blade 21p alum. I bolted that on and it barely gets on plane. Just bogs the boat out. It also has a much lower cruise rpm. The dented prop cruises nice at 2900. The same nice cruise on the same pitch Apollo is 2700.

Huh????

ric · **Posted:** Sun Aug 11, 2013 2:31 pm

How is this possible?? Both 21p. The Apollo has a top speed of 4000 rpm. The other one is 4600.

Walt · **Posted:** Sun Aug 11, 2013 3:16 pm

cavitation.

Try a 19P

Winter Sux · **Posted:** Sun Aug 11, 2013 3:25 pm

Wrong diameter. :lol:

deafwish · **Posted:** Sun Aug 11, 2013 4:33 pm

There are many different factors in prop's design than simply pitch!
Rake, cupping and hub diameter play a crucial role in how they perform.
I'd doubt an educated man like yourself would've bought a replacement prop' just on it's spline count & pitch?!

ric · **Posted:** Sun Aug 11, 2013 11:06 pm

It came with the boat. I know there's differences but god dam. That's insane.

Walt · **Posted:** Mon Aug 12, 2013 4:43 pm

It is tough to compare two props "apples-to-apples" because of the reasons above. Diameter is rarely the same, and changes dramatically with pitch AND blade count. Also, some will have vent holes to allow air at the leading edge of the blade, others do not.

I think iBoats has a really good listing in that you can see the different diameters, pitches and blade counts all in one set of tables.

rpengr · **Posted:** Mon Aug 12, 2013 10:16 pm

The "other" prop could have been re-pitched by a prop service to something less than 21p.

It is also possible that wear and tear, or the impacts that gave it some dents also reduced it's pitch.

ric · **Posted:** Mon Aug 12, 2013 11:17 pm

When I purchased the boat the 21p prop was perfect. We had a dry spell and the water levels got danger low. In that time I ran aground a few times damaging the prop. I have it off now kinda fixing it in my spare time.

I think the spare is repitched. It looked new but the black paint came off very spotty almost instantly. There's no way in my experience that two 21p 3 blade aluminum props could have nearly a 600rpm difference. I'll measure it.

Not sure what came from the factory, I'm waiting on the answer off the chap forums. Their past specs are not as accessible as four winns. I'm 99% positive it was a 4 blade.

ric · **Posted:** Wed Aug 14, 2013 2:15 pm

Turns out my boat requires a 14.5x18p 4 blade.

Other chap 215 5.0 owners said their boat also came with a 21p 3 blade aluminum and it was horrible. Barely breaking 4000 rpms and 40mph. Real dog out of the hole. They stepped it down to the 4 blade 18 pitch and they're getting 4800rpms and 50mph GPS and they rocket out of the hole.

Dang. If I didn't just order that table I would buy the correct prop!

Kvou812 · **Posted:** Sat Aug 17, 2013 3:19 pm

I believe I have the same motor you have...5.0 and 14.5x18 4 bladed SS prop is what I went to from the original 14x19 3 bladed aluminum prop. Much better whole shot....a little loss on the top end but thats not a concern for me as I mainly host a lot of folks while pulling tubes and boards.

www.iFourWinns.com

two 21p props. act totally different

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