Knowing your noises

When we returned after some years working in Brazil I would be doing something in the garden (for example) and suddenly become aware of a noise coming from a distance, a repeating sort of whistle. It would be impossible to tell the direction and I could only guess at what it was – electricity cable perhaps, or some strange burglar alarm. It was really annoying and frustrating not to be able to identify it. It was only months later that I discovered that the legislation had been introduced requiring large vehicles to have an alarm when they are reversing. The sound would come across the summer evening air from many roads away. It's all about knowing your noises.

Philip from Oxley Marine knows his noises. As we did a test run on Erin Mae a couple of days ago he was commenting on nuances from the engine and drive gear that I couldn't even distinguish. But when we tied up last night I could hear a whistle in the air. It wasn't our fridge. I thought it might be the guy in the boat moored thirty yards away doing some DIY. Then I thought it might be some farm machinery – this was a really rural mooring. I ignored it while I played my guitar on the towpath, and we got our evening meal and watched a fascinating programme about Stradivari. As I began to shut up Erin Mae for the night I realised I could still hear the noise, especially when standing on the cruiser stern.

So I lifted up one of the deck boards over the engine, and the noise got louder. It definitely seemed electrical – a cross between a kettle whistle and humming from a dodgy piece of solder. It didn't sound at all healthy. So I turned off the starter battery isolator – no change. Turned off the domestic battery isolator – no change (except that all the lights and the fridge went off). Checked the battery bank for a short circuit, but it didn't seem to be coming from there, and I couldn't see any sparking in the dark.

It was when I went to the main electrical control panel to see if there was a switch for the diesel central heating unit that I found the answer. The bilge pump was turned on, instead of to "auto".

It's the sort of thing a boater who knows his noises would have thought of immediately. It implies that the bilge pump is wired to be connected even when the battery isolator switches are off, which makes sense and is probably in Erin Mae's manual. It's the sort of thing I should have guessed, ever since we turned off the water pump by mistake during an early cruise, with a hand misplaced as we came down the steps.

Well, that's one more noise identified, to be filed away for future reference, along with the reminder to be careful where you put your hands. Glad we got it before we completely drained our new batteries.