Isolator switches not isolating

[sprocker]

Our MF645 has two batteries (I assume one for engine and one for house), and two isolator switches (One for each battery).

What I don’t understand is that with both isolators turned off, the ignition still works, the engine trim/tilt still works, the VHF still works, and the bilge pumps still work. I can kind of understand the bilge pumps still working, but they are manual only with no auto switch.

My idea of an isolator switch is that it does just that, it isolates. If I turn each switch off at the end of the day it protects the batteries against any drain etc.

Could it be that the isolator switches are faulty? Or incorrect wiring? Or am I misunderstanding something here.

[ColinR]

Normally you would have either two switches or a 1-2-both-off arrangement. If the batteries are in the off position I would expect to mean exactly that although it makes sense for maybe the bilge pump to be always on.

Sounds wrong to me.

[_Ed_]

Sounds wrong to me too. You should definitely not be able to run trim pumps etc.

[mlines]

Our bilge pump, radio memory backup and trim pumps are live when isolators are off.

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[_Ed_]

Trim pump requires a heavy supply. I don't really understand that. In the event of an elec fire or something I'd want everything to be off! Wonder what the reasoning is for that.

[mlines]

This was true of both boats we have had

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[_Ed_]

Need to investigate why now! Very curious indeed.

[mlines]

On the latest boat we have a transom trim switch so standing behind boat you can trim without any power
The throttle trim switch is also always live

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[Ianfs]

Have you also got another battery separator switch? And a bus panel with various switches?

If so, check the separator switch is turned to off.

As the guys have said, we get that your bilge pump is a permanent live feed and maybe the radio for memory but not the ignition/starter circuits and some have transom switches too, so you don't have to climb in a out to flush/trail etc.

[sprocker]

Have you also got another battery separator switch? And a bus panel with various switches?

If so, check the separator switch is turned to off.

As the guys have said, we get that your bilge pump is a permanent live feed and maybe the radio for memory but not the ignition/starter circuits and some have transom switches too, so you don't have to climb in a out to flush/trail etc.

I'll pop down to the Marina one night after work and double check for the other switch. I don't remember seeing a bus panel with switches, just the fuse panel.

The trim switch on the actual engine is also live permanently.

We do have shore power with charger fitted, so I'll take a closer look in the cupboard and see what I can find.

I don't remember if our last boat had live trim pump or not, but would appreciate knowing if any other outboard owners do.