The Lehman engines do have pencil zincs which are located in the heat exchanger, it is suggested that they be checked on a weekly basis while the engines are in service. I believe that the reason for accelerated erosion of the zinc while at the marina has to do with your neighbors boats not being grounded properly to shore power, thereby, seeking a ground through your boat. The installation of a ground isolator should resolve the problem. Paul -----Original Message----- From: Garrett Lambert [mailto:e16@telus.net] Sent: Wednesday, January 17, 2001 11:25 AM To: TWL Subject: TWL: Electrolysis One of the freebie boating booklets suggested last Autumn that shore power should be disconnected from boats being left in the water but not used regularly to guard against electrolysis. As I understand it, two different metals immersed in an electrolyte such as salt water set up a current between them without any need for external stimulation, and the lesser metal erodes. Since zinc is, to coin a phrase, a "least metal", adding sacrificial zincs means the current flows to and erodes them rather than some valuable and essential component of the vessel. I assume, therefore, that the recommendation to "unplug" simply removes a possible source of accelerated deterioration. However, the latest threads on zinc placements got me wondering. How do you determine where zincs should be placed, how big they should be, and when you have enough of them? My boat has "brush" arrangements on the propeller shafts. How effective are they? Finally, could someone tell me if Lehmans have pencil zincs and if so where they are located? Cheers, Garrett