Who has lost their prop cup?

[AirTool]

In all my boating experience, this ACME 422 is the first "cupped" prop I've ever used. I'm wondering how oftern you guys have the prop re-cupped or checked even if you don't have any "damage".

[TRBenj]

What type of boats have you had in the past that ran props with no cup? Every inboard ski boat prop Ive seen dating back to the late 60's has had some cup in it. My buddy has a larger inboard fishing boat that some people like to run without cup- but thats a pretty different application.

I am not aware of the need to ever check the cup unless you damage the prop. I assume you could point out the cup if you were to hold the prop in your hand?

[AirTool]

What type of boats have you had in the past that ran props with no cup?

Mercruiser I/O and outboards ....all with aluminum props. We saw many stainless props cupped. But none of the props we had (aluminum) were cupped.

Several folks have told me it is possible for the cup to fold back (mainly due to grounding in hard soil). Just looking at my prop the cup is not obviously lost...but each blade doesn't feel/look the same. It is very hard to tell though.

[CradGen2]

Air - do you have a vibration in the boat?

[DanielC]

The cup on a propeller influences the effective pitch of the propeller. Adding cup has a similar effect as adding a little more pitch to the propeller. RPM's drop for the same speed, usually. If the cup on one blade looks significantly different that the other blades, there is a good chance your propeller is not running as smooth as it could.

There are many other factors on propeller design that affect how a propeller runs. Cup is only one.

I doubt the cup on a nibral propeller can be changed if it only contacts water. Damage from sticks, ran over skis, rubbing the bottom of the river may damage or change the cup, but the propeller is usually bent on more areas than just the cup.

[mcbridek]

I have the 422 prop and mine had a slight bend in one of the blades, by guess is from hitting a log that was under the surface. I just sent it to be repaired. On mine, you could feel a slight vibration at lower speeds, but at 32 - 36 MPH you could tell something was off - both the sound and the vibration. If you stack a few blocks 2x4's of wood so the top block is close to the bottom of the blade. Mark a reference point on the wood. Slowly turn the prop and watch the reference point against each blade - you can see any problems. Of course if you hit something hard, like a rock, it is very apparent. But if you don't hit anything, the prop will not need any work - there is a boat next to mine at the ski lake, 422 prop has 750 hours on the original prop and the prop looks fine - a little pitting in the valley between the blades from use - but it's fine.

[AirTool]

During the flashes of the island, Daniel and Desmond had an exchange in which Desmond was the costume of hazardous materials. Jeremy Bentham's coffin is revealed the true identity of Jeremy Bentham, in a scene that shocked and surprised the spectators.

That's great....kinda what I was thinking. That is precisely why I posed the question. I'm hoping the PN spectators are equally shocked and surprised.