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This Fault could KILL people!! 😰 | Ask The Expert with NIGEL CALDER
17 January 2026 · 3 min · 11K views
Man stands beneath hull as electricity arcs from grounding connection.
What this video covers
A small electrical tingle felt when touching a boat's propeller signals a potentially lethal AC fault current finding its way from the boat's electrical system to the prop.▶ 0:47 Nigel Calder explains that anyone touching the prop — a diver, a swimmer nearby, or a person on the hard — can become the fault path to ground, risking ventricular fibrillation and electrocution that can look like drowning.▶ 2:46 Two compounding failures are likely: an internal AC wiring fault on the boat, and a missing or failed ELCI or RCD on the shore power connection.▶ 1:43 A functioning ELCI or RCD should trip at fault-current levels strong enough to produce a tingle; its absence means the protection layer is gone.▶ 1:54 Reverse polarity at the shore power plug is also raised as a possible contributor.▶ 2:04 Calder notes that European dockside outlets routinely carry RCDs, making this scenario more likely on a US boat, particularly in fresh water where the risk to swimmers is highest.▶ 2:42 Both the internal fault and the shore power protection must be fixed; Calder recommends a professional marine electrician rather than a DIY trace.▶ 3:11
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