Why put the battery isolator in the -ve line?

[GARYOFFSHORE]

?????Does sea water not pass through the engines you are refering to? Are you sure they totally isolator from the sea??? Are the engines not bonded to the anode at all!!! Am I missing something here??

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[GARYOFFSHORE]

?????Does sea water not pass through the engines you are refering to? Are you sure they are totally isolated from the sea??? Are the engines not bonded to the anode at all!!! Am I missing something here??

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[MainlySteam]

It does not matter if the engine is isolated from the sea or not, if the engine is not connected to any other metals in the sea with an electrical conductor then there is no purpose in bonding it (unnecessarily bonding it would be connecting it to other metals and possibly opening up a can of worms). Protection of the engine, as a result of the metals within their own construction, will be incorporated in the engine by its own anodes if required (many engines have no anodes of their own because they do not need them).

What people seem to forget is that if a metal is in seawater and it is naturally resistant to corrosion then it does not need anode protection if it is not electrically connected to another more noble metal, also in seawater. If the engine, whether it is a DC isolated one or not, is not connected to other metals in seawater then what galvanic harm can it come to?

John

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