1999 Proline 17' center console. Original Faria gages (0-7000 rpm). Mercury 100-125 Hp 2 stroke outboard. My tachometer is frozen at 500 rpm. All my other gages work and I have checked all connections in the back of the gage cluster for tightness and connection. I removed the cowl on the engine and all wires appear to be attached with no obvious signs of loose wires or bad connections. What would be the next thing you guys would look at. I am at a loss. I bought the no joke Mercury engine repair manual hoping it would give some wire diagrams that would help. No such luck. Are there any "idiot checks" that I might do that might save me a lot of time and money? Any ideas are greatly appreciated. I've been lurking here a while and really appreciate all the priceless info I have gathered up to now. Maybe one day I will have valuable input to put in, right now, I barely know the difference between my butt and a hole in the ground.