Electrical Loads from Ignition Switch

Electrical and electronic topics for small boats
pcrussell50
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Joined: Fri Oct 16, 2015 1:08 am
Location: SoCal/SoNev

Electrical Loads from Ignition Switch

Postby pcrussell50 » Fri Aug 07, 2020 12:42 am

I was under the dashboard of a boat today solving a electrical wiring problem that was "installed" by my otherwise superb mechanic.

(It's not germane to my question but if you are curious, the fuel gauge would work when you turned on the Perko master power switch, but would drive back to zero when you move the ignition switch to "ON". I solved that one easily enough).

Is it "ship shape" to power the red and green sidelight lamps and the white all-round lamp ( which each have a simple 12-Volt bulb) from the same power source that powers the instrumentation, the ignition switch?

Or should I have the navigation lamps be powered separately from the ignition switch?

Is it okay to power the tank selector solenoid through the ignition switch?

Or is that bad form?

-Peter

jimh
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Joined: Fri Oct 09, 2015 12:25 pm
Location: Michigan, Lower Peninsula
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Re: Electrical Loads from Ignition Switch

Postby jimh » Fri Aug 07, 2020 7:21 am

Generally an outboard engine ignition key switch provides some extra electrical power for engine-related accessories when the key is in the RUN position. This electrical power comes from a fused circuit that originates at the outboard engine. The circuit is typically fused for 10-Amperes. The wiring for the circuit is typically part of the engine electrical harness that runs between the helm and the engine.

The usual accessory loads that operate from the ignition key switch are limited to engine instrumentation, such as a tachometer gauge, a fuel tank level gauge, a trim gauge, and perhaps gauge illumination circuits.

Loads such as lamps for navigation lighting would normally not be powered from the ignition key switch accessory circuit because the ignition key switch would have to be in the RUN position in order to illuminate the lamps.

I am not sure what the electrical load for a "tank selector solenoid" would be.

Usually a separate power distribution circuit would be run to the helm from the primary power distribution at the stern of the boat. This secondary power distribution would typically be run on conductors of 8-AWG or 10-AWG wiring, and provide power to a fused secondary power distribution panel at the helm. This circuit would be protected by a fuse at the battery; the fuse rating would be appropriate to the total electrical load that will be powered from the circuit, perhaps 20-Amperes or more. The power panel could be something as simple as six fuses circuit and a common ground bus.

For concise advice about boat electrical wiring see

Boat Electrical Circuits and Wiring Practices
http://continuouswave.com/whaler/refere ... iring.html