I have a Westerbeke W46 and the pencil zinc seems to have broken off in the heat exchanger. I was going to remove the heat exchanger so I could remove the end caps, clean the zinc bits out, and clean out the tubes while I'm in there. I can't figure out how to drain *all* the coolant from the block. There is nothing in the manuals. I'm assuming there is a plug bolt somewhere. It's been suggested to just drain at the hot water heater hoses, but that does not seem low enough to drain what's in the block. I don't know how long the coolant's been in there, so I figured I'd replace it while I clean out the heat exchanger. Maine, I saw your pics of the Westerbeke heat exchanger you rebuilt, so I figure you must have the skinny on what I at first thought would be an easy job. -Tom