Gauges Install

Hi, I am installing a voltmeter and tach on my 83 50hp merc. I guess I am wondering how to install these gauges. I hooked up the voltmeter to the red power wire leading to the ignition switch and the ground to the black and it read the battery volts, but the concern was that the key was in the off position and it seems that a gauge hooked up with the battery hooked up would eventually run the battery dead. Also I have been told this motor is a 12 pole and I bought a group of gauges off ebay with no info on the tach. It says no brand, all it says is it was made in like 1979, it has a blue case and a +, -, and P connectors and a little dial on the back that says 4, 6, 8. I tried all these settings and on four it read nothing and on 6 and 8 it read on 6. I had this gauge connected from the P to the grey wire in the motor harness, the + to the red wire and the - on the black wire. This gauge goes to 6 but says x100 instead of 1000. I am assuming that it would still work though as I know of no engine that can only max out at 600 rpms. Any help would be appreciated as I am heading to the lake tommorow. Thank you,
Chris

Re: Gauges Install

You might want to check your wiring concerning the color gray,from my wiring diagram the gray wire goes to the choke and the brown wire is for the tach/pulse.As for your tach you might have the wrong kind of tach.

Re: Gauges Install

The +12 volt lead from any gauge should be connected to the "A" (accessory) terminal on the ignition switch -- not the red +12 volt INPUT to the switch. "A" is active only when the key is in the RUN position.

Re: Gauges Install

Your tacho is an auto tach or one for inboards. The 4, 6, 8 is the number of cylinders and it means its for a 4-stroke engine. Your 83 Merc is no doubt a 2 stroke so you won't get that tacho to work Just sell it and buy one for an outboard. Ebay is a good place to find some. I have a Faria tach on my Mercury 2 stroke. They seem ok but not had it for very long. Your tach will read something if its hooked up to the pulse wire (usually grey?) and a +ve and -ve but the readings will be incorrect.

I'm a novice on these kinds of things and find the manual is your best bet for wiring colours. get one from ebay on a CD or similar and check out the wiring diagrams for your engine. Like I was advised by silvertip the other day, only hook your gauges to the 'hot wire' in the wiring harness. That way they will come on when you turn the key. On my harness its the purple wire I believe. Just get a Multimeter and test it out. Will only take 5 mins