[C320-list] Propeller Shaft

[Jack Brennan]

These bronze shafts usually are made of naval bronze for cost reasons. This means they’re not really bronze, but heavy-duty brass, because they usually have about 40 percent zinc mixed in with the copper. This is the same for most bronze props,  through hulls, rudder shafts, etc.

The way you tell whether the naval bronze is going bad is that it turns pinkish as the zinc leaches out from corrosion, it being the least noble metal in the alloy.

I’m sure many of you have seen this with bronze props that weren’t properly protected with zincs. The surface also will start flaking as the corrosion grows more severe.

If the naval bronze is perfectly smooth and not pinkish, and if it has been properly protected with zincs, I’m going to argue that  the shaft is fine. 

Jack Brennan
Sonas, 1998 Catalina 320, no. 528
Tierra Verde, Fl.
Dolphin Cruising Club of Tampa Bay