propellor protection

[hobbit]

I have removed my propellor in order to renew the cutless (or cutlass?) bearing. On haulout I had already noticed that the shaft anode was missing. It has probably fallen off sometime suring last season, when I experienced a vibration problem with the engine. The propellor was sandblasted clean, and subsequently showed numerous pittings and surface defects. Now the integrity of the thing is not yet in question, but I would just like to know:
1) Is this most likely due to galvanic erosion (the propellor is bronze - what kind of bronze you ask?)
2) Should it get worse over subsequent years, is there any method to repair the defects?
3) Is there a grease or vaseline that can be used to mount the propellor (and propellor nut) onto the shaft to make the removal process next year easier, or is a pure metal-to-metal contact the best way to ensure electrical continuity btw propellor and shaft?

Frodo


PS: I made some pretty clear close-up pictures of the propellor, which I would be happy to email to anybody who thinks it might help their diagnosis

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[ccscott49]

Pitting of props is often caused by ventilation and cavitation, but if your prop has a definite copper colour, it could be de-zincafication. Does the prop, ring like a bell, when tapped with a baby hammer? Difficult to tell you how it should sound, but a dead thunk, is an indication of de-zincing. The fact that your anode is gone is also an indication something is not quite right on the electrolysis front. I`d get the prop checked by an expert also the balance, as you mention vibration and also check my anodes and electrical system, for "leaks". Copper grease on the taper and nut will be fine. The prop can be repaired if its cavitation pitting, but not if it`s de-zincafication. IMHO

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