Confirm my choice - cart before the horse

[ChasR]

After looking at several posts I decided to buy a new Michigan Vortex 4 blade alum. prop 14 x 20. The goal was to reduce cavitation, quicker plane and lower plane speed.
The boat -
98 Reinell 203LS
Weight approx 3000# with normal load
Power - 5 liter by Volvo @ 220HP
Recommended WOT 4400-4800
Volvo Penta SX-M Cobra Sterndrive

Current prop is a stock 14.25 x 21" 3 blade which gives me 50 mph at 4800 rpm. (17% slip?)

My question is? Did I buy the right prop? I figure on losing a little rpm (about 150) but reducing slip.
Anyone like to debunk my thinking?
Thanks
Chas Robertson

 

[junior1113]

Re: Confirm my choice - cart before the horse

not going to lose many rpms if at all. your supposed to go down 1" in piitch when adding a blade to keep rpms close to the same. i think youll be happy with it though. and slip should decrease some. better hole shot, fuel ecconomy, acceleration. the best part is you can be on a plane at slower speeds than a 3 blade. and i honestly think you might pick up some top speed. good luck

 

[hwsiii]

Re: Confirm my choice - cart before the horse

Chas, what is your gear ratio.

H

 

[junior1113]

Re: Confirm my choice - cart before the horse

cobra sx-m has 1.79 gear ratio

 

[hwsiii]

Re: Confirm my choice - cart before the horse

Thank you Paul.

H

 

[ChasR]

Re: Confirm my choice - cart before the horse

Sorry to be so slow, servers were busy.
The ratio listed for the Volvo Penta SX-M Cobra is 1.60 which seems on the low side but is written on the drive.
Chas

 

[hwsiii]

Re: Confirm my choice - cart before the horse

Chas, I will run some numbers for you.

H