On May 17, 7:16 am, nick wrote:
Hi All.

I don't know if anyone can help with suggestions here but I'll give it a
whirl.

I hauled out my boat last week to do the bottom paint and discovered
substantial blistering of the paint. I attacked these with a high
pressure cleaner initially and that stripped most of the loose paint off.

In places bare metal was exposed, in others it was back to the primer or
undercoat. It was particularly evident around welds and through skin
fittings (metal ones only) and even around the anode bolts.

Nick it could also have been a bad priming job before or when the
barrier coat was applied. Paint over dew ect...ect.. The welds are
always areas that harbor moisture.

Could also be stray voltage from a nearby fiberglass hull effecting
your hull. You would be suprised how many idiots use car type battery
chargers without grounds to keep the batteries charged. I've seen
zincs boiling on glass boats before.

Are you zincs welded on or bolted?

I had a shipwright and a very experience boat painter look at the hull
and both confirmed a stray current problem, albeit relatively minor.
Interestingly, both said I had TOO MANY anodes on the hull and that this
in itself can cause a problem.

I have since done some quite extensive reading on the subject on the net
and in some books and all confirm the diagnosis.

So, armed with a multimeter I set about doing some testing but first a
basic description of my electrical system.

The boat has a large house battery and a decent engine battery plus 180
watts of solar panels. The engine has a standard alternator (30A I
think) plus a heavy duty 120Amp alternator mounted on it.

The engine is isolated from the hull via rubber engine mounts.

No it is not. It will make contact with the hull via the shaft and
shaft tube.


snip


Any suggestions?

As others stated, turn it all off and measure, power up one at a time
and measure.

Good luck, let us know what you found.

Joe

Thanks for any assistance.
Cheers,
Nick.