Stray current and engine grounding.

[Simi 60]

Had sparkies onboard last week checking us for stray current as on the last slip we had a bit of blown paint due to a poor grounding plate and connection.

They suggested we fit one of these when out which i did , redid the grounding wire and they said its better to give the boat some time to settle down before rechecking.



On the check it was noted a slight discrepancy between the rudder and the engine and grounding them was recommended.
After a look around they said running the ground for engine off of alternator negative was as good a spot as any but now I am second guessing them.

I have the gear now and i am running a hefty tinned cable from rudder post to ground plate and from engine to ground plate.

Instead I was going to use a cleaned up bolt sticking out of the block, as one usualy does when connecting earth to engine, theory being that the alternator , due to what it does, may have more chance of actually introducing current to the water than a bolt on the engine.
Plus I feel a bit uneasy about having an integral part of the engine wired up in this way.

Thoughts?

[Sailmonkey]

Depends, is the alternator case ground? If not it’s a pointless exercise anyway to attach the bonding there.

Given my choice, I’d attach to a clean stud on the block, or to the earth connection of the block if your not operating an isolated ground engine.