Bow thruster zincs Electrolysis

[northshoreone]

Background, I pulled the boat in Jan. to have all the old bottom paint removed for a fresh start and to address any blisters that may be hiding under the old paint. I also had the bow thruster pulled to rebed it to the hull as I had some seepage around it. The zincs on the thruster were being eaten faster than any others already then. We found that it wasn't bonded to the grounding system of the boat properly. In the process I added new grounding cables bonding it too the boat properly. My diver was on the boat cleaning the bottom and reported the bow thruster zincs were all but gone with the rest of the zincs looking fine! When I return to the boat next week I will recheck the thruster bonding but my question is.....if that is not the issue what else could cause such electrolysis to occur with only the bow thruster zincs? The boat also has a stern thruster and those zincs are fine along with all other zincs on the boat.
FYI the bow thruster is a Wesmar which runs off a separate 24v battery bank.
Thanks for all thoughts concerning the issue...