My hull is alive

[shaungonemad]

Hi folks when I got my boat I was doing some wiring repairs and I found that some of the earth wires were grounded to the hull. I have since run a new main wire to a buzz bar with all the earths running off it but the hull is earthed, Could this be from the motor or somewhere else that is not insulated ?
PS I hate wiring especially after someone else has played with it. The boat is a 2007 Horizon Getaway with a 130 yamaha 2 stroke.

[Axl]

I think you will find that all alloy boats have a current in them as the motor bolts directly onto the hull, the +VE and -VE leads go from the battery to the motor so when the isolation switch is closed/turned on (if you have one) it livens up the hull as well, happy to be proven wrong but that is my understanding.

[shaungonemad]

Ok that could be the case I have heard people say not to earth the hull?

[Axl]

That is correct DO NOT earth anything to the hull of an alloy boat make sure everything is earthed back to the battery, if this isn’t the case it will speed up electrolysis.

Electrolysis is happening already in most alloy boats with batteries due to the hull having a small current in it but if you earth to the hull it will increase the rate at which this is occurring.

[shaungonemad]

Ok that makes sense now thanks

[daveo17]

i had the same problem with my old stacer. caused a lot of electrolysis and made a couple of my switches short out. not good for the boat get rid of it.

[Crocodile]

Hello Shaungonemad,

Comments from an amateur boat electrician.
I did some re-wiring and carefully used earthing wires and was annoyed to find that the hull was still earthed.
Yes, it was the motor bolted to the aluminium hull.
Nothing can done about it.
I now disconnect the battery negative when the boat is not in use.
I have tested with a multimeter and no current or continuity.
The good news is that my boat is 17 years old and has very little corrosion so maybe it is not a major issue anyway.