The shore power inlet carries the boat's heaviest load through a single plug, and a poor connection turns into heat. Tom Hale, a former technical VP of the ABYC, writes in SAIL that when the failure is at the boat end, the heat, smoke and fire are inside the boat.
Why it overheats
- Corrosion. Salt on the blades adds resistance. Hale calls corrosion friction in the electrical circuit, and notes it often starts when a cord end has been dropped in the water.
- Arcing. Plugging in or pulling out under load arcs across the blades, and each arc leaves them worse.
- Loose fit. A locking ring left undone lets the plug work loose.
- Heavy loads. Hale notes these fires often happen in winter, when heaters run for hours.
The temperature check
Run a heavy load, such as a heater or water heater, and measure the connection with an infrared thermometer. Hale's thresholds:
| Above ambient | What it means |
|---|---|
| 2 degrees | All is well |
| More than 10 degrees | A problem has started |
| 20 degrees | Time to act |
He suggests owners check several times a year. An infrared thermometer costs from about USD 20, per SAIL.
What else to look at
The blades and the socket face for brown scorching or melted plastic, the cord's plug for matching damage, the locking ring and the cover. From inside, look at the back of the inlet where the boat's wiring attaches, for discoloured insulation or a loose terminal.