Propeller "color." ??

[MikeP]

I don't know anything about props other than where they go/how to install them so I have a question...

About two years ago I had the yard change props while the bottom was being painted/new cutlass bearings were installed. The props were my spare set of original Hatt props that came with the boat. They had never been used and were still wrapped as originally supplied. These props were "bronze/brass colored." I don't know what the actual prop material is. I assumed they are bronze but I don't know that.

But yesterday, when diving the boat/cleaning shafts/props/installing new zincs in Oxford, MD, I noticed that the props are very grey colored, not bronze/brass colored at all. Actually, I noticed that the last time I replaced the zincs last season. In both cases the zincs were still there though appropriately eroded

So...what causes that color change?

 

[Blaine Thorpe]

Any chance they are becoming electroplated by the zinc from the anodes?

 

[MikeP]

I was wondering that but I don't know enough about the chemistry involved. The props that used to be on the boat were non-OEM and different pitch, installed by the PO. They always looked brass/bronze colored. Since nothing else has changed, I think I'll just ASSume that it's just a difference in the prop material. It does SEEM like these props do not get anywhere near the amount of barnacles but maybe local wx/water conditions varying from season to season has resulted in fewer barnacles rather than any difference in the prop material.

I have noticed that there never seem to be any barnacles on the zincs...

 

[SeaEric]

When you last had her hauled and bottom painted - did the yard spray the running gear with the gray Pettit paint that keeps the barnacles off? http://www.defender.com/product3.jsp?path=-1|2200442|2200447|2200452&id=157662

 

[MikeP]

Hmmm...the shafts have clearly been painted but that looks like the regular bottom paint. I didn't request that the props be painted with the Petit so I assume they did not.

One thing that occurs to me now is that since last year I put out two zinc "guppies" when we are away. Maybe that much zinc - two guppies plus the normal zincs - is "plating" the props? I don't know if that can happen or not.

Maybe I need to do some chemistry 101 since I can't remember anything from when I actually took Chemistry 101!

 

[Avenger]

My boat's underwater metals were heavily zinc-plated when I did my first major haulout. Scoops, ground plates, props etc. It took hours of bead-blasting to get it off, and I strongly suspect that the narrowing of the slots on the generator R/W intake was responsible for the original generator's demise.

 

[SeaEric]

Hmmm...the shafts have clearly been painted but that looks like the regular bottom paint. I didn't request that the props be painted with the Petit so I assume they did not.

One thing that occurs to me now is that since last year I put out two zinc "guppies" when we are away. Maybe that much zinc - two guppies plus the normal zincs - is "plating" the props? I don't know if that can happen or not.

Maybe I need to do some chemistry 101 since I can't remember anything from when I actually took Chemistry 101!

Just a thought: Before you begin an extensive analysis of the metals and their chemistry, You may want to check your invoice for the bottom painting.