Prop Zinc Wear

[MikeH]

My port prop zinc is wearing at 2 to 3 times the rate of the starboard zinc.

I had installed a new one 10 days before I hauled out - the zinc was already pitted at haul out.

The zincs are from boatzincs.com.

Any ideas?

[deising]

Going from memory, I believe that faults in the shore power wiring can introduce an electric field in the water. The field is strongest nearest the underwater fault, so in the unlikely event this is your problem, is the port side closer to the shore power? A good marine electrician can test for you.

OR, it could be something else entirely that I cannot think of at the moment.

[chrishead]

Not related to pitting, but worth sharing is our experience with premature prop nut anode failure and fit. Our former tug used the same prop nut anodes. Some tug owners including us experienced the anodes becoming loose on the nut due to more rapid perishing where the allen bolt secured the zinc to the prop nut. Once loose, the zinc would wobble causing vibration until it eventually fell off unless tightened. The recommended fix was to put some paint (or something to insulate) inside the bottom of the zinc around the mounting hole where the zinc would sit against the nut to prevent premature perishing. We also found that the zinc didn't fit snugly on the prop nut and would wobble until tightened. Inserting pennies inside the zinc on opposite sides to make better contact with the nut seemed to help. We got two seasons out of our last prop zincs on the PDQ, but we mostly anchor out or hang on moorings.

[duetto]

a suggestion. if you search this site you'll see a modification to the nut which significantly cuts down on the loosening problem. basically, install a screw from the inside of the nut and then use a nyloc nut to secure the zinc. otoh, if you don't have line cutters, you may want to consider switching to prop-shaft zincs with conventional prop nuts.

[chrishead]

Thanks, John, I'll check it out. We do have line cutters, so shaft zincs aren't an option.
Chris