Instrument panel and tachometer went out

[jsakat1]

Last time I took my boat out my tachometer wasn't reading -- as where my other gauges. But the tachometer has been acting funny. It doesn't go all the way down to zero. With the engine off, the needle points at 1000 rpm. Has anybody encountered this? Do you guys know a way of checking if to see if it operates properly or what could be the problem.

We, my father and I,  opened the panel, and for some strange reason the postive red wire was connected to the negative terminal in the back of the tachometer. Once loosened that wire, the needle went down to zero. Howerver, when we ran the engine and turned it off it stayed -- off at 1000 rpm. Please help

[GoneFission]

What kind of engine is it?  It makes a difference - some tachs don't read zero with the the power off...

[jsakat1]

1985 Mercury 75 HP is the engine I have.

[GoneFission]

It is normal for a Mercury tach to read 1000 or almost any reading with the power off.  It reads off the stator and is not entirely tied to actual crankshaft revolutions like a mechanical tachometer; it's more like hte basis for how many times the magnets pass the pickup.  It should drop to zero with the power on and the engine not running.  

If all the instruments went out, you've probably got a loose connection on the hot side - assuming they are not all grounded to the same lead.  Check the fuse and the power (+) to ground and see if you have about 12 volts.  Check the ground wire(s) as well - wiggle them around a bit at see if the ground is intermittant.  

Hook the tach up as the specs require and you should get the correct readings.  Mercury/Quicksilver tachs are pretty trustworthy and durable, so you can usually trust the readings.  

Hope this helps!

[jsakat1]

Thanks for the help I will look into that. I took the boat out on Sunday. The tachometer was working, and other gauges worked too other than the water temperature gauge.  It has not gone over 120 degrees. The water coming out of the engine didn't feel 120 degrees hot, but for the six hours the engine was running I would think the water temperature gauge would pick up.