Originally Posted by mark-f
I am just picking up a new merc optimax and asked for an isolating switch be fitted and was told they would fit it but if there was a faut in the charging cct or electronics they thought there would be trouble with the warentee if one was fitted as even having it isolated and switching it on whilst the engine was running could cause a spike that could either damage the engine or the electronics on the boat. :-(
I annoys me when so called professionals (outboard dealers / riggers / boat sales) completely miss the point and show themselves to be ignorant.
All boats should have an isolation switch between the battery and the engine / services.
The switch should not be switched off when the engine is running - this will damage the alternator and possibly other engine electronics.
The switch cannot be switched on with the engine running as it would not have been possible to start the engine with it in the off position.
The only thing that should not be switched should be the bilge pump.
Presumably your boat will be/is CE Marked? Part of this requires that the electrical system is safe and the most common way of proving this is for the system to comply with the relevent ISO standard. This requires an isolation switch.
Perhaps you would be better off buying your engine from someone who knows what they are doing.