BoatHowTo · video

What this video covers

Corrosion on a saildrive housing despite an intact, unused anode indicates a failure in the electrical bonding between the anode and the drive leg.1:04 Nigel Calder explains that Volvo Penta saildrives utilize a plastic gasket to galvanically isolate the drive leg from the engine, preventing the unit from becoming an anode for the rest of the boat.1:06 In contrast, other manufacturers connect the drive leg to the engine block, which often links the leg to the boat's DC negative and external grounding circuits, leading to accelerated corrosion.1:29 To diagnose a failed connection, use a multimeter in ohms mode to test resistance between the anode and the saildrive while the boat is hauled out.2:41 For Volvo Penta units, a low resistance reading between the engine block and the transmission indicates that the galvanic isolation has failed.2:22 Testing the electrical continuity of the anode installation ensures the zinc is properly grounded and capable of protecting the aluminum housing.2:43

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