Galvanmic corrosion?

[John7]

I have a multimeter reading of 0.02 to 0,03 Volts with the boat batteries removed. The only bonding is the link from the GM10 to return and to the main sacrificial zinc, about ¼ gone this year.. The GM10 zinc was ¾ gone when I checked it, with just less than 50 hours used this year with the boat in the water, sea, for 8 months.
Is this sort of level normal for a 1GM10 or do I have something wrong and need of attention?

 

[ccscott49]

sounds totally normal to me. I would expect that the engine anode would suffer, it's a little one and in contact with lots of different materiails, so setting up more disimilar metal corrosion.

 

[John7]

Thanks, I thought it might be bot though I use a multimeter to keep an eye on the battery voltage I hadn't used it to read the current with the batteries off and then removed before.