BoatHowTo · video

What this video covers

A viewer measures 0.6 volts between a gearbox and a propeller shaft on a boat fitted with a flexible coupling and asks whether the elastomer insert is conducting rather than isolating.▶ 0:27 Nigel Calder explains the coupling itself is not the source — a properly installed rubber insert does not conduct.▶ 0:49 The more likely explanation is that zinc or aluminum sacrificial anodes on a stainless steel prop shaft impress a small galvanic voltage across the system, which a meter will pick up even with the coupling in place.▶ 1:04 Calder notes other system factors could also produce the reading and that further investigation is needed to identify the exact source.▶ 0:58 The key point: a 0.6-volt reading in this location is not a cause for concern and does not indicate a faulty or conductive coupling.▶ 1:37

More from BoatHowTo

ONE SWITCH for TWO PUMPS?? (Pontoon Boat Setup) | Ask The Expert with NIGEL CALDERJul 2026OIL LEAKS at the Crankshaft... | Ask The Expert with NIGEL CALDERJul 20261-2-both switch - Cost effective charging system on small boats? 🤔 Ask The Expert with NIGEL CALDERJun 202648V or 24V - What makes more sense on a Boat? | Ask The Expert with NIGEL CALDERJun 2026

From BoatHowTo — see the channel’s boat, crew, and every analyzed video.