Brass Propellers - Too Thin?

[rwidman]

Certainly, your prop is not made of brass. Brass will fail pretty quickly in salt water. Your prop is bronze, nibral or another alloy.

As for "thinning". when I had my boat surveyed in 2008, the surveyor noted that my prop was thinning due to electrolysis (not being polished too often in a boatyard). I have put nearly 3,000 hours on it since then with no ill effects.

 

[psneeld]

For those that might have missed it....

https://www.passagemaker.com/channels/dont-fall-for-the-brass-line

A dezincified brass propeller can be identified by its splotchy reddish or pink coloring. Contrary to popular belief, many propellers are fabricated from a brass alloy (by definition, in order to be considered a true bronze, a copper alloy must contain little or no zinc) and, as such, are especially susceptible to dezincification.

 

[bil56]

the main problem is mainly the color :
if your propeller turns pink or even red, that's serious!
it becomes brittle and the slightest shock on a piece of wood, a chain or a rope, and it may break clean.
propeller turned pink/red means poor anodic protection ...

./;

 

[DaveGibson]

zincs

I always put zincs on my prop shafts. Cheap insurance.

 

[stevemitchell]

I just replaced my bronze 3 bladed props a couple of months ago due to thinning. In survey 4 months prior we noticed pitting in areas, and the overall condition was fair. When she was hauled in March 2022 to have some other work done, I chose to replace the props with new 4 blade bronze props due to the thinning. The Prop Shop (local folks in Mukilteo, WA that many folks in the Puget Sound use) were able to refurbish the 3 blade props, but they are noticeably thin, and they theorize that they will flex more as a result.

The other driver for switching to 4 blade props was because of the size of the 3 blade props and the horsepower/weight/other calculations that benefit better from a 4 blade setup.

 

[Reelhappy]

I bought my Cape Dory in Mississippi and it ran smooth with no vibrations but when I got her home to NY I had her pulled and sent the wheels to the local prop guy. The moment he looked at the props he said they were worn to thin and flexing under load. He put the props on the bench and actually flexed the blades by hand. Replaced them with the same size in Nibral and picked up nearly 2 knots. So it is real

 

[RustyPBucket]

The prop looks to be turning red which is a sign of weakening from electrolysis. If you tap it with a hammer and it rings you should be good to go for a while longer. When I tapped mine it was just a thud. Totally dead. Was told if I had even a minor strike there would be a good chance of a prop failure. I replaced it.
Even as red as mine was the edges still didn’t show any signs of thinning or chipping.

 

[OldDan1943]

Brass?
You sure about that?

Bronze

 

[psneeld]

For those that might have missed it....

https://www.passagemaker.com/channel...the-brass-line

A dezincified brass propeller can be identified by its splotchy reddish or pink coloring. Contrary to popular belief, many propellers are fabricated from a brass alloy (by definition, in order to be considered a true bronze, a copper alloy must contain little or no zinc) and, as such, are especially susceptible to dezincification.

 

[OldDan1943]

The prop looks to be turning red which is a sign of weakening from electrolysis. If you tap it with a hammer and it rings you should be good to go for a while longer. When I tapped mine it was just a thud. Totally dead. Was told if I had even a minor strike there would be a good chance of a prop failure. I replaced it.
Even as red as mine was the edges still didn’t show any signs of thinning or chipping.

This is the result of a failure of the bonding system.
Worse case, blade breaks off and into the hull.

You could hunt around for a stainless prop. I am told, with the proper alloy, your problems should be over. Alas, I don't know the proper alloy. I suspect the prop shop can provide you the good points and bad points of stainless prop other than the expense.

 

[JRO]

Don’t give it a second thought… Get a new bottom man.

 

[RustyPBucket]

This is the result of a failure of the bonding system.
Worse case, blade breaks off and into the hull.

You could hunt around for a stainless prop. I am told, with the proper alloy, your problems should be over. Alas, I don't know the proper alloy. I suspect the prop shop can provide you the good points and bad points of stainless prop other than the expense.

That’s what I did. There was lots of props around bur none with a 2” bore. Found a used SS one in nice shape and took it to our one and only prop guy. After lots of discussion and he tiddled it up to give me what I needed. He had to change the pitch. Works well. Put an anode on the prop nut, added a galvanic isolator to the system and a bond from the shaft to the bonding bar that is hooked up to an anode. Hopefully it all helps. Will see next year when I bring it up.
I have seen props here that have the blades half eaten away and a couple that looked like Swiss cheese.