Mark James

Hi, thanks for all of your responses. In answer: - Mark99, yes, we had anodes and they were shot to sherry when we took the boat out - but then it had been 8 years. We doubled up this time round and will look again next summer. We have ordered some new fenders (we never bothered for about 2 years as didn't mind the (minimal) bumping) - not realising we had opened ourself up to this! - thanks for the link, Catweasel. Also, yes, it's a car type aerial (that has never tuned properly), and i'm taking it out pronto. We have a wind-up radio that works fine anyway. - we haven't checked the voltage differential between the bank and hull, but the surveyor recommended an earth strap to equalise this. However, someone else said that that would guarantee we were part of the circuit. - And bacteria!? Jeez. I'm ringing Brian Cox tomorrow... Thanks again for your help.

Hi We recently had our boat out of the water for blacking (6 years overdue on an 8 year old boat) and were pleasantly surprised that, despite the passage of time, the hull sides were in excellent condition. The deepest pit we found there was 1mm, which was a relief as we were expecting much worse. Now, we're the proud owners of an almost 11mm bottom plate and when we had a survey done it was found to be pitted in places up to 4mm deep. This of course took the smug grin off our faces. The colour of the metal was bright silver (and we definitely didn't fork our for a boat made of silver), which we were advised suggests that the pitting is 'new' and quite likely to be stray current corrosion, (although the prop was as good as new, except for a dint or two on the edges). We don't use shore power, or even use a generator, or an inverter, excepting a small 150w Maplins bought inverter for charging the phones of guests who need unusual plugs, my cordless drill and an LED rechargeable torch. This inverter plugs into the 12v cigarette lighter socket that we have as part of our DC system. I have a million questions and am after a bit of a steer. What we know - We moor against metal (steel?) pilings and until very recently, without fenders. - The DC supply that we have is connected from the negative on the starter battery to the engine block, as is the starter motor (i think) - Multimeter tests confirm that the engine is in some way connected to the hull, although we have confirmed that this is not through the prop. Haven't had a chance yet to see if it's the exhaust, and the engine sits on rubber bearers. - Haven't had a chance yet to go through the electrics to see if there is a stray positive connection directly to the hull, although i'm fairly sure that our radio aerial is. The electrics were installed thoroughly, this side of a layer of sprayfoam insulation and are all cable-clipped to the wooden battens, except under the gunwhale on the port side where they're clipped to the inside of the panelling where it hangs below the gunwhale. All negative connections run right back to the batteries. The horn, tunnel light and nav lights obviously go through the steel, but within rubber bushes and i'll be checking them at the weekend. - Western Power Distribution have provided a cable map showing overhead power cables approximately 250yards from our mooring and a cable that runs across the canal about 50yards away. I am awaiting their response as to whether the latter runs under the road on a bridge over the canal, or under the canal. - There is a sports club nearby which has power, but as yet we don't know where the supply cable for this runs (again, awaiting WPD's response) - We are not negatively bonded to the hull, possibly excepting through the engine. What we don't know - Can DC current cause this severity of corrosion? (loads of contradictory info) - Should we bond the negative to the hull? - Should we wear wellies for bed? Apologies for the length of this and thanks for reading. Any advice anyone can offer would be gratefully received. Thanks Mark