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Author Topic:   Electrical Wiring
simon posted 04-04-2001 07:12 PM ET (US)   Profile for simon   Send Email to simon  
how am I able to figure out which instruments are working off the engine's alternator while running. I haven't had any problems with electrical power or the battery.
lhg posted 04-04-2001 08:43 PM ET (US)     Profile for lhg    
Not sure I exactly understand your question, but on outboard powered Whalers, all engine instrumentation is wired off the ignition harness of the engine(s), not "house" power. Depending what you have installed, this would include tach, volts, hours, temp (cylinder head temp), trim position indicator. A water pressure gauge and Speedometer are mechanical, not electrical, except for the lighting. Gauge lighting is usually also wired off the ignition, where it goes on automatically when the ignition is on. But some prefer to wire it off the house circuit and navigation light switch instead.

All other electrical equipment on board would be wired off the "house" power, but which is still charged off the engine alternator.

Incidentally, on larger Whalers, powered with older twin engines (usually mid range engines), the alternator charging capacity can sometimes be inadequate for today's on-board electronics, etc. You can draw down more power than the engine is providing, especially at trolling/no wake zone speeds.

simon posted 04-04-2001 08:53 PM ET (US)     Profile for simon  Send Email to simon     
great input, thanks. I am installing a bait pump and I want it to run off the engine while running. I do have a panel/fuses in the center console with connections from, what I think is coming from, the motor. I
triblet posted 04-04-2001 10:24 PM ET (US)     Profile for triblet  Send Email to triblet     
My Montauk came from the factory with the
instrument lights wired with the navigation
lights (not the anchor light). Makes sense
to me:
- No sense consuming power during the day.
- No sense wearing out the bulbs during the
- It's a good reminder to turn the nav lights

I can't offhand think of any reason to wire
the instrument lights with the ignition.


lhg posted 04-05-2001 12:05 AM ET (US)     Profile for lhg    
Chuck: You make a good point. I think this is one of those things that's up to personal choice, or ease of installation.

I assume you mean your boat came with OMC factory pre-rig, and it is interesting to see how the factory is now doing this. I wonder how they're doing the Mercs with total package from the factory? Maybe someone can add to this.

The reason I ask is that all Mercury OEM gauges come with a built-in "link" that connects the light to the ignition automatically. So when the key is on, the light is on. As the gauge cluster is wired instrument to instrument, this eliminates a lot of extra wiring and work. Merc does say, however, that this link can be removed if one wants to run wires to the lights separately. I have 6 gauges on each engine, so by using Merc's system I avoided a whole string of extra wiring. The bulbs seem to last forever, and I think I have only replaced one or two in 15 years. Also, the heat keeps the instruments dry. When fog/moisture inevitably gets in, it disappears in a few hours. I have recently re-rigged my older 1986 Merc OEM gauges (still have some for sale!) with the new Teleflex domed glass Pro Series, and they are terrific, with really cool red lighting. But they did not come with the Merc style "links", with instructions instead as you are proposing.
So I made a little jumper wire on each gauge instead to accomplish the same thing. I guess that's what I'm used to.

I've never even thought of how much power the gauge lamps consume. Don't have the slightest idea, but with the 40 amp alternators on my 200's, I'm not too concerned about this. My 115's only have 9 amp output, so maybe those would be more affected.

jimh posted 04-05-2001 12:09 AM ET (US)     Profile for jimh  Send Email to jimh     
Unless you have a second battery which is completely isolated from the engine, anythng wired to the battery or wired to the engine's "ignition" circuit is all wired together.

Electricity flows quite nicely in either direction, so if the battery is higher voltage than the engine, the current it drawn from the battery. If the engine (really its alternator/charger) is creating greater voltage than the battery, then the engine will supply the current.

Or have I misunderstood your query?

Chesapeake posted 04-05-2001 11:28 AM ET (US)     Profile for Chesapeake  Send Email to Chesapeake     
Would it make sense to NOT wire the bilge with the ignition as you want it able to run when the engine is not.

I have got to re-wire the basics of my 16 this weekend in preparation for new motor delivery. I had planned on running everything to a new fuse box (Blue sea 5015). Is this a mistake?


lhg posted 04-05-2001 01:50 PM ET (US)     Profile for lhg    
Bob, to the best of my knowledge, only engine instruments are wired off the engine's ignition harness, where leads are provided. Bilge pumps, never.

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