wiring steel boat

[shantymanuk]

I am a concerned about earthing to the hull in relationship to cathodic reaction , with plastic lights etc can one just use live and nuetral without earthing to the hull and keep the lot seperate from the hull ????

 

[Anchorite]

Put nothing down to the hull...are you talking about 230v or 12 volts (the answer is the same). For the 12v system best practice is motor isolated (mounting blocks and flexible coupling should be non-conductors): a marine alternator has an earth terminal (doesn't rely on the motor frame for the earth) but this doesn't matter if you have a car alternator + motor isolated from the hull (needs careful checking...).
What are "plastic lights"? /forums/images/graemlins/tongue.gif

 

[Norman_E]

12 or 24 volts I do not see any problem with avoiding earthing to the hull providing that your engine and alternator connections do not automatically result in the hull being connected to the negative side via the engine and gearbox mounts.
Shore power current is a different issue and I think you need a qualified electrician to advise you. My concern is that the mains will be earthed, therefore your hull in the water will easily make a circuit with the mains earth.

 

[shantymanuk]

thanks for your replys ,i didn't make myself clear , the engine is an outboard,and not connected to the hull in any way , and I won't be using shore power ,so I take it all is ok to for the system not to be earthed to the hull ,as i had suspected ,but not having anything to do with a steel hulled vessel before was a bit out of my depth as far as they are concerned

 

[shantymanuk]

nav lights etc are plastic cases,with internal metal connectors,and no metal connection to the hull or bulkheads etc .

 

[Norman_E]

I had just assumed that a steel boat would be fairly big and inboard powered. If all you have on board in electrical terms is 12 volt stuff you are in no danger of electric shock so earthing is not required. It does not mean however that you can be any less vigilant as regards galvanic corrosion, and anodes need fitting and checking regularly. Unlike a fibreglass or wooden boat your hull is potentially an anode if there is a more "noble" metal in electrical contact with the steel hull and physical contact with the water.

 

[shantymanuk]

hi norman thanks ,its a steel silhouette ,in fact the last known steel one , I have put anodes on the bilge keels ,and i dont think there is any other metal other than mild steel ,in the water , may be a little stainless on rudder shaft and rudder fixings ,but other wise nothing as far as i know ,she is 40 years old this year, and the hull doesn't show any signs of rusting,pitting or anything else ,completly stripped her back to barte metal ,and all perfectly sound ,a bit of rusting in the cockpitt but thats all .