Originally Posted by 9D280
The other option is disconnect the lead to the mount bolt & let the anodes do their job alone.......
That will remove any "external" influences. Also your Engine should be connected to the _ve by the starter cable somewhere under the hood. If not and it;s connected to the mount bolt, I would imagine to get power to anything useful inside would need a lack of paint under siaid bolt........
Thats what I got the impression of, The battery negative connected only to the transom clamp?
That would be a good way of inducing electrolytic corrosion. Battery negative should go straight to the starter motor or star earth point or near to it as possible, so no current flows through any part of the engine/leg.
where a current flows there will be a voltage drop, and the electricity will take an alternative path, ie out of the rams, into the prop/anode carrying a little bit of the ram with it, up the leg to the powerhead.
also if your lead only goes to the transom clamp the steering bearing and tilt bearings will be carrying current which won't do them any cood. They are bypassed by a small earth strap, but thats to prevent corrosion by bonding across the very high resistance bearing, theyre not designed to carry current, theyr'e thin, and stainless which isnt a very good conductor so could fry up when you crank the engine on the starter.
Technically the transom should be bonded, but in reality the chances of it not being with four tight m12 bolts holding the engine to it are slim.
if it is bonded it should be to the clamp and nowhere else that could be at a different potential, even if it is only 0.1 volt over time it will take its toll