prop question 3 or 4 blade and update

[Barry Pase]

It's been a while since I've stopped by

I'm the guy that has a 640LX with a 50hp and after a lot of hassele from my dealer I finally have a 90hp (4-stroke)



1st thing I have to say is it's like having a new boat. Hole shot is great and improved top end. It is a lille heavy for the boat but other than that I'm a happy camper!!!



Now the prop question...



Currently I have a 12-3/4 x 21p.

WOT 5400rpm, gps 49mph.



I decided to try out a piranha prop.

They recommended their 13x21b.

WOT just a shade under 6000rpm, 48mph gps. Seems to be working a little to hard



Now they recommend a 4 blade w/20p as the next step.



Any thoughts on this one or recommendations? Never tried a 4 blade before.



Thanks,

Barry




http://www.piranhapropellers.com

 

[Michael Snow]

I belive the pirhana props are the composite ones, right? The FLEX is your reason for lower speed and higher RPMs. Also, the hub size impacts this. A 4 blade TYPICALLY will help you plane faster but also usually gives you lower top end. Not so on my HEAVY 911, as it has better hole shot but equal or better top end.



Stainless steel won't flex as much as an aluminum prop. Be careful what you pay for a prop... check www.jacosmarine.com for pricing, just to make sure you're not paying too much. Locally, the prop I can get for $400 from jacos, the shops want $500-600.

 

[Bill Willette]

I have the 640LX with a 90HP 2-stroke and run a

Laser II 22P (I think its 13.25 dia), best run by

myself is 49.1MPH(GPS)@5500PRM. This is really

kicking butt for a 90HP. What was wrong with your figures

with the orig prop? Are you sure it's not a 12.75x23P? Thats what was installed on my 90HP originally. I tried a

stilleto 13.25x23P stainless but it dropped the RPM's down to 5200 and the hole shot was not as good (top speed was the same). Thats when I exchanged it for the Laser II stainless 22P. All the above props were 3 bladers. I got the Laser II from Reynolds Racing and Marine on the internet for $325. They had the older Laser II's also (without the vent plug system and rubber bushing hub) for $295 but I wanted the newer Flow-Torg hub. I'm not sure what you'll get by going to a 4blader with a 90HP, it might get a better hole shot but lower your top speed.