Prop - Cup or not to cup?

[tmdog]

Pros and cons of cupping a prop. Why cup a prop? Will cupping increase rotation torque? Will it raise or lower stern at moderate speeds? Will cupping compromise ride quality?
I responded in a prior thread (what prop on 18)of a terrible ride at speed I experience with a 23 Mirage+ that is cupped in semi rough water. Other members state there 18 rides smooth in the rough water. Am I missing something? Need help. Thanks, Jim

[mikev]

from what i understand cupping a prop will improve the holeshot but thats about it.

[tmdog]

I heard the same thing Mike, That the cup helps prevent slipping when throttled. The other symtoms remain a mystery.

[Tony]

I hope it is good, since I had a slight cup added to my 21" and 23" aluminums, and even my 24" SS Volvo Ultra. My guy says it helps holeshot, midrange, AND top end...all with no disadvantages! I didn't see any snake oil on his shelves as a sideline product, so I'm giving it a try.

I'll let you know soon the opinions from this camp.

[BillG]

Cupping increases forward thrust by directing the water straighter aft. The Ultra already has a cup unless someone had it removed. I have never run any boat without a cupped prop and have never had any adverse effects. The Ultra on my 18 is the best prop I have had up until something better comes along.
Bill G

[MOP]

All of the benefits Bill mentioned are true, I won't run anything I have without a cup. Another point a cup is about equal to an inch of added pitch. Sometimes you have to pull a little pitch off to add the cup.

[jwright]

I have been told that the purpose of cupping is to distribute the pressure more evenly across the face of the blade. This allows a small diameter (smaller surface area) to be used without cavitation.
Just another peice of info to mull over!

[Donzigo]

Cupping props on a larger boat........like my 1989 Z-33. Any advantages?

She's a beast to get on to the step, then she flys.

[MOP]

Donzigo the cupped wheels will bit better at any speed, not sure if that is what a heavier boat needs. You may be a little better off with a bit of slip to let it turn up its RPM to get into its power band. I ran a Switzer with a step we tried a few different props but could not get the bottom end performance up but like you said flew once up and going.

[Throttle Up]

Just thought I would add a bit about cupping. Cupping results will vary depending upon the placement of the cupping as well. As you increase cup you will decrease RPM. Your can also change the way the bow carries as well as the transom by adjusting the cup in different places on the leading edge.

Julie
Throttle Up Propellers
877-842-6855