Propeller root cavitation

[Adnan]

One of our boats got out of water recently. The propellers are generally ok except that it has very significant root cavitation erosion. Can anyone indicate possible causes and remedies. Pics below:

 

[steelespike]

Sure looks like electrolysis to me. Either an issue within the boat or possibly a neighboring boat or an issue within the marina.
Someone posted almost the exact same problem the other day.
I have two Aluminum props with fairly severe cavitation issues both look like someone took a power wire brush to them.
Yours looks like a Bronze prop in salt water that could lose a blade from corrosion.I'm pretty sure it could be brazed.
Perhaps the outfit needs a sacrificial anode.Looks like you have a Bronze prop a stainless shaft and a bronze strut.
possibly 3 different metallurgic combinations.Look for stray voltage,A poorly grounded devise or circuit.
Perhaps an ineffective sacrificial anode.

 

[alldodge]

:welcome: to iboats

I don't see it as cavitation, if it was there would be burning signs on the tips of the blades. This looks to me as impurities in the bronze when manufactured. Bronze is made in most cases from nickel aluminum bronze alloy. High strength bronze I find also has iron added to them. Need to find a prop shop with the tools to repair

 

[Adnan]

Thank you guys for your comments.

As AllDodge said if it was cavitation there would be signs on tip of the blade. But if it was material fault should not there be some failure signs on the blade root on the leading side as well? The marks are only on the trailing side of blade root.

Can it be that it is a design flaw which results in very low pressures on the trailing side of the blade roots?

 

[alldodge]

Thank you guys for your comments.

As AllDodge said if it was cavitation there would be signs on tip of the blade. But if it was material fault should not there be some failure signs on the blade root on the leading side as well? The marks are only on the trailing side of blade root.

Can it be that it is a design flaw which results in very low pressures on the trailing side of the blade roots?

Need a fluid dynamics person and that's not me. My opinion would be that it may just be a manufacture flaw with the prop, and my guess would be due to impurities when pouring the prop. Don't know how many of these type boats you have but if it's happening on all of them I would ask the manufacture of the boat, and again another source would be a top rated prop shop like Bblades

 

[Scott Danforth]

is the issue evenly on all 3 props?

 

[Adnan]

I cant say about other boats before they are docked, but the problem is on both the propellers. Anyway I was inclined towards AllDodge's opinion. So we changed the propellers today. I will get in touch with the manufacturer about it.

Thanks guys, esp AllDodge, for sharing your knowledge. It was great help.