Question about Prop lapping

New to me 2006 SV 211 Last year.
Been messing around with props trying to decide which one I like better.
The original prop that was on the boat (856) got a bit of a ding in it first time out this year, so I had it rebuilt. I had a rebuilt (644) backup prop that I bought form NP over the winter, so I put that on. I plan on taking the boat to a church function where I will be pretty loaded next week so I decided to put the fixed 856 back on.   I did the lapping procedure found on this site both times. I also came across a screaming deal on a "never used" 644 prop so will probably sell my rebuilt one. I am also doing some testing with RPMS to see which prop I like better (644 vs 856). My questions are: Is there a limit on your shaft as to how many times you should lap a prop.   Once a particular prop has been lapped and then removed, does it need to be re-lapped? Just wondering since I have been playing musical props here lately.

My theory is that when you lap a bronze propeller onto a stainless shaft, the softer metal propeller is going to be the half of the equation that does the actual dimensional change. This is purely speculative since I’ve never measured the very small changes that occur in this very low speed lapping operation.

I think you can lap to your heart’s content. I like the idea of the very cheap brand new 644! That sounds like a real nice find.

8122pbrainard wrote: Peter, I think you should look up some material Rockwell harnesses.

Pete, we machine Nibral impellers as well as stainless steel impellers on a production basis all day long. There’s a whole lot more to wear pairs than hardness. Lapping is an abrasion process where the compound does the work, not the metal to metal action. It takes a lot longer to lap the shaft bore of stainless impellers than the bronze. 😏