Heat Exchangers

By Don Casey

When did you last replace the zinc pencil inside your engine's heat exchanger? If you don't remember — or worse, if you are thinking "the what?" — this is a maintenance job that needs immediate action. The copper tubes inside the exchanger are at risk of damage from electrolysis — just like your prop. An internal zinc anode protects the exchanger. You will normally find the zinc pencil under a threaded plug near one end of the exchanger. If it is only lightly corroded, scrape it bright and put it back; if it is heavily corroded — or gone altogether — replace it. Check it at least annually.

Don Casey has been one of the most consulted experts on boat care and upgrades for 30 years, and is one of the BoatUS Magazine's panel of experts. He and his wife cruise aboard their 30-footer part of the year in the eastern Caribbean. His books include Don Casey's Complete Illustrated Sailboat Maintenance Manual, and the recently updated This Old Boat, the bible for do-it-yourself boaters.


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