how to wire 55w running lights?

I need to run a pair of 55w lights on the bow of my duck boat. These will only be used when running (never left on) but I don't know if I need to run them off of a separate battery from my starting battery or not. The battery is only used for 25Hp cranking. Can it handle it? If not, and I do need to add a battery, is it as straightforward is it seems? Switch in the back near the tiller, a panel to ground it? Is that it?

Thanks in advance,
Brent

Re: how to wire 55w running lights?

You don't need a ground panel. Positive terminal of the battery goes to a fuse, then to the switch, then to both hot leads on the lights. Ground leads from both lights goes to the negative terminal of the battery.

Whether or not you need a separate battery depends on how big the starting battery is, what the alternator output is, and how long you run. 110 Watts at 12V is roughly a 10 amp load. We have no idea how old or new, or what make 25 HP outboard you have but I would guess it has about a 6 amp alternator. That means running wide open with the lights on alone you are using 10 amps but only putting back 6 maximum so the battery is discharging at a 4 amp rate. I would at least carry a jump start pack and in a pinch a 25 is easily rope started.

I can't wait to see the responses to this plan!

Re: how to wire 55w running lights?

110 watts will flatten a battery fairly quickly, it's akin to leaving you cars headlights on (motor off). Battery size and (more importantly) charging system will determine if you need to pull start the motor at the end of the day (or in this case, night).

Unless you under dash wiring is suitably setup for heavy load accessories, I would run twin 8 gauge direct from the battery (or battery switch) and install a 15 amp fuse close to the battery, the ground can go directly to the lights, the positive runs through a 15 amp switch on the dash.

The wire sizing depends on load (110w) and distance between the load and the battery. The longer the distance, the greater the wire size. There are plenty of wire sizing charts floating around on the net so you can do your own calculations but bigger is always better.

Re: how to wire 55w running lights?

Brent, check your local regs before running with anything other than "running lights". Those lights are probably illegal to run.
I have them myself. hehe
If you use Ohms laws, watts divided by volts
110 divided by 12=9.17 amps
you could run a TOTAL of 11.5 feet with #10 wire.
up to 18 feet with #8
Any questions just post em.
And by all means, please fuse the circuit. (in the hot or positive wire)

Re: how to wire 55w running lights?

"Brent, check your local regs before running with anything other than "running lights". Those lights are probably illegal to run." agree, most states it is illegal. it blinds any on coming boaters.

Re: how to wire 55w running lights?

this is flooded timber running on WMAs, so the only folks ahead of me are in my group and there's no looking back at 4 a.m. It's an all out race. Those guys that come from up north to hunt with us can't stand to watch, so they lay down in the bottom with the dogs.

anyways...
1998 Mercury 25 tiller and a 6.5 amp marine battery. we aren't required to run our red/green running lights, so two 55w (after starting) is all it'll be powering. This alternator will make it up for the next restart IF I power off the lights and let it idle as we putt along, right?

Brent
Arkansas

Re: how to wire 55w running lights?

If you really have a 6.5 amp battery, those lights will kill it less than an hour. Remember what I said about losing ground even with the engine running? You could leave it running constantly at wide open throttle and it will continue to lose ground. Just because you have an alternator and a battery doesn't mean you can keep up with the electrical demand when that demand is greater than the supply. Sort of the same reason people go broke. They spend more than they make. In your case you are using more juice than you can make.

Re: how to wire 55w running lights?

Are you hunting ducks or trying to cook them with those lights?
Seems to me I saw spotlights rated for 250,000 candlepower that only draw 20 watts
Are 2 - 55 watt lamps really needed?