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View Full Version : Ign Harness GND vs Batt GND



tj309
03-20-2006, 08:12 PM
I am totally re-wiring the boat since I am redoing the dash panel. The ignition harness and key from the Merc outboard has a black wire (among many more) which of course is ground. Is the ground direct from the battery the same? Can I use either interchangeably?

Problem is instrument lighting - some gauges like the tach have a + input for the light and use the Ign GND for the neg part. Other gauges like the mechanical water pressure gauge have both a + and - for the light only. Other gauges like the clock and depth I want to wire to a separate switch so they can work all the time and I dont have to set the clock every time I re-start the motor - so these need a switched + from the battery and a - from the battery(?) or Harness GND(?)

Thanks, TJ

bigbore
03-24-2006, 05:12 PM
lights need to be on a switch in the dash panell(don't want a light drain on the battery in the day)(obviously + connected to the switch)
like i say with the ground,it needs to be constantly connected,just run a ground from the battery up behind the dash pannell and use that for all the grounds.:cool:

Tom D.
03-31-2006, 09:44 PM
I use a grounding bar out of an typical in home electical panel to make multipule connections to the dash. The purple from the harness on one, 2 wires direct to the battery 1)+ 1)-. Hope this helps.

Tom

150aintenuff
04-15-2006, 03:16 PM
do it right.. go get a fuespannel / busbar combination and run a 8 ga power and ground from the batery will only cost ya about 30 bucks for a 18 circut pannel that has a sealed cover and uses the blade type fuses bluesea among others bulids them... and can be bought at any marine supply, donot use a fuse and swich pannel combo limits the number of circuts you can put in and takes up more room than a seperate panel with wires running to your swiches in the location you want them. and all grounds must be tied into your battery in some form.. either through the switch or a bussbar, otherwise you have no current flow.. and when your done heres a test to do, take a DVOM and drop the ground lead in the water and the positive lead to any grounded section of hull, any more than .2V and you have a grounding problem with your boats wiring and electronics, even in a totally aluminum boat with several brass and stainless steel pieces i can get the DVOM to read less than .1V and all of that is galvanic voltage as i can remove the batery and the voltage moves less than .005 V..

Fast Fred
04-15-2006, 03:55 PM
ground is ground. and thats that.:cool: make it neat, clean and nice,
so if someone ever looks under thare thay say "that's nice" insted of " somethin else":eek: :cool:

150aintenuff
04-15-2006, 04:11 PM
make it neat, clean and nice,
so if someone ever looks under thare thay say "that's nice" insted of " somethin else":eek: :cool:


that should be a requirement...

tj309
04-15-2006, 05:22 PM
Mine is a work of art.... Too bad no one will see it.

150aintenuff
04-15-2006, 05:32 PM
take pix.. that way it can be on display...