Maxprop growth - from a leaky current - not algae.

[jpeac2]

All -

Have a three blade folding maxprop on my 1997 35' Beneteau.

When it was up on the hard this year we noticed what looked like growth on the prop. Not from algae but instead it almost looked like cement. A boat neighbor saw it and said it is from a leaky current somewhere in the boat.

We used some chemicals and a flat headed screwdriver to chip away it but dont think I got all of it.

Someone then suggested I replace the anodes with magnesium ones to help with this.

The boat is only used in freshwater.

2 questions:
1. Having never replaced the anodes - are magnesium the right ones?
2. Can these be replaced while the boat is in the water or does it have to come out to make the change?

Any other guidance here? First time working through this.

[Sailmonkey]

We change anodes in the water all the time, of course our mean time between haul outs is 5 years. IMHO, magnesium anodes are the correct material for fresh water.