Aluminum boats and zincs

[Steve B]

I have a few questions about mounting zincs on a 20ft. painted aluminum boat with a wood reinforced transom. The zinc on the transom wasn't wasting at all. It was through bolted at the bottom of the transom, and upon removal I found the bolt holes had been eaten away leaving me to wonder if it was making any contact with the hull. So, my questions are...

1. What size of zinc is right for this boat?
2. Should the paint be removed from the mounting area to provide good
contact, or is contact from the bolts securing the zincs sufficient?
3. What is the best way to seal the mounting bolts without interfering with
the zinc to hull contact?

Any information on this subject would be appreciated, as I am trying to prevent this otherwise great boat from eating itself alive.

Thanks, Steve

[Mo Betta]

1. What size of zinc is right for this boat?
The bigger the better, it will eat itself down eventually

2. Should the paint be removed from the mounting area to provide good
contact, or is contact from the bolts securing the zincs sufficient?
Yes remove the paint, you need more surface area.

3. What is the best way to seal the mounting bolts without interfering with
the zinc to hull contact?
I always sealed from the inside, using a marine sealant. Dont use 5200, there is another on that is easier to remove when its time to change out the zincs.

Make sure you didnt drop any copper wire cuttings down in the bilge, and keep it dry. Frank