Engine zincs replace 2007

There are two pencil zincs on Nevermore's engine. Both are shown in the

A: Old pencil zinc removed from the heat exchanger (the heat exchanger moves sea water over cooling tubes which have circulating fresh water, which in turn cools the engine.)

The little chunk was found inside the heat exchanger, along with several very small (like sand) pieces of zinc (and/or possibly actual sand?)

B: New pencil zinc installed Fall '07; we found two of these aboard Nevermore in the box of new spare parts.

C: Old pencil zinc removed from the oil cooler (the oil cooler moves sea water over cooling tubes which have circulating engine oil, the same oil used to lubricate and cool the engine.)

D: Old pencil zinc found aboard Nevermore; it's the same size as (B), so we assume it was removed by previous owner, but at unknown (to us) time.

E: New pencil zinc we bought, ready to be installed in the oil cooler (Jan08); we had to cut down its length (we discuss this below, but note that its zinc is longer than the heat exchanger zinc, whereas the oil cooler is smaller diameter than the heat exchanger.)

F: Another new pencil zinc for the heat exchanger, presented here to show the different size of item E zinc. We bought it (West Marine) to compare to the units we found aboard (see item B.)