Earthing the electrics


New member
25 May 2004
Ashtead, (Office Heathrow Airport)
I am going to replace some of the earth leads in my wonderful Trapper. At the moment they are all led to a strap that is attached to the keel bolts.


Should I remove this strap and reroute the leads to the various anodes that are all wired together?

Many thanks


Well-known member
30 Jun 2002
This is not as simple as it sounds. If you mean the negative terminal of your battery is connected directly or indirectly to a keel bolt then remove it or you are likely to cause electrolysis in the keel bolt.
The correct arrangement is to keep the negative isolated from the hull entirely. The anodes should only have a direct connection to the equipment they are protecting.
However, where a propshaft is electrically connected to the engine and thereby to an anode connected to the engine block, which is a common arrangement nowdays, the engine block being connected to battery earth is connected to the anode indirectly so the anode will be battery negative anyway. This is not a preferred arrangement but has to be recognised to exist on many small craft. If this is so in your case it would be better to move these connections to the anode as you suggest. Even better it would be ideal to have them terminate at a common point (say the engine block) and then isolate the engine block from the propshaft and anode. In this case you will need an anode on the propshaft itself if you have room or a slipring connector on the propshaft to connect to the anode to protect your prop.