redson

I own a 34ft Glacier Bay catamaran 17,500 lbs. with twin counter rotating Verado 275's. I have 2 sets of SS 4 blade power tech props 14". The best performing set tops out at around 5580rpm (varies some with weight) the other set gets up to 5900 rpm but is less economical at cruise and has a lower top end speed.

At 3500rpm I am getting 15.9 mph 36% slip ,4000rpm 20mph 30%slip ,4500 22.5mph 30% slip ,5000 25mph 30%slip, WOT 5580 29mph 27.5%slip .

The props are the smallest pitch I can find 4 blade SS. The slip seems too high and therefore less efficient and/or lower performance. If the slip was reduced by 50% to 15% slip the rpm’s would be even lower with the same prop pitch and the rpm is already too low.

What can/should I do?

bbladesprops

Give us a call when you can. We may have some options including working the Powertech propeller you currently own.

crb76

Merc Rev 4 worked well with mine. Brett knows them well. He got me 7mph over the bravo.

throttleup

Well 17,500 lbs is a big girl...Diameter may be key in your application.

Julie

redson

I have taken a set of the power tech props to naples propeller and they scanned them and found the pitch varied between each blade. The plan is to repitch all blades to 13" add 3" of additional cupping to the tips, he feels that a progressive pitch is not required since the hole shot is fine.

If this does not work I plan to buy a new set of mirage plus 15.75" x15p , test them on the boat and send the props and results to have them reworked to 13" double cupped and shaved .

Does this make sense?