Speed loss expected when going from 3 to 5 blade

[QBhoy]

Guys,

Would like to think I'm pretty well up on propeller dynamics and issues 30+ years experience with fast boats (or as much as one can be on the black art or prop selection, haha) and I'm terribly aware that all boats respond different to different props, even unexpectedly ! So I ask the following question in the hope that people who have done the proposed can give me their experiences with similar set ups and circumstance. Even if you haven't, I would like to hear opinions and educated guesses from forum.

I can't complain with my current set up, having the slip rate as about as low as it gets, but I'm wanting to get back into a bit of watersports this year and would like a prop that isn't too much of a compromise when not wakeboarding and water skiing.
The obvious candidate is a Hi 5 prop. So the question is how much top end will I loose when going from the tried and tested laser 2 to this ? Will it be minimum enough to be able to leave it on all season.
All the above is asked when keeping the same pitch of 19".
Thanks.

 

[alldodge]

More blades equals more lift, more lift in the stern can cause the boat to porpoise. A 19P 4 blade is more like a 17P 3 blade, sort of.

With water sports I don't think your going to like it

 

[Sea Rider]

Is OB running with current 3 blade prop 19 pitch at max wot rpm range factory stated as usually loaded ? Post max wot rpm ?

If going from say a 3 blade 19 prop pitch to a 4 blade will need to go for a 18 prop pitch, if going from same 18 pitch for a 5 blade prop will need to go for one less pitch to a 17 to theoretically maintain same wot rpm, that's what's being said..

If maintaining same 19 pitch on all 3-4-5 blade props will achieve different wot rpm and consequently different top speeds. Don't know if there's a single prop for overall excellent water performance under different boating applications aside from a variable prop pitch.

Happy Boating

 

[QBhoy]

Thanks Alldodge and searider, valued opinions as always.
Should have given more details....
Don't fancy a 4 blade, the diameters tend to be larger (from what I've seen)
Was really specifically talking about the hi 5 specialist watersports prop. I'm sure I read somewhere that the same pitch (if you already have the 3 blade prop ideally suited) can be used.
Most of last year I used the all round suites 3 blade 19" laser 2.
This allowed the boat to reach 60mph at around 5050-5100 rpm. It would occasionally hit the limiter if allowed to just after this. Prop slip was about 4 from memory at this...which is pretty damn good ! I can't ask for more than that really, but would love to see what the high five can do.
I did run a few times with a 21" laser 2, which was really fast at about 64mph on occasion at about 4800rpm or there abouts (from memory). The boat wasn't as happy or as good an allrounder in general though. Much better with the 19".
I'm just wondering if the high price of the high 5 is worth the investment.

 

[jimmbo]

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