Help! Tach problems

[spareparts]

Frem is correct about the crank sensor giving the tach signal, it goes thru the ECU and the computer generates a tach signal for the tach to read. Easiest way to diagnose it is to hook another tach to it. I don't care for the yamaha digital tachs, they are expensive and seem to only last four or five years, I'm old school, I like dials and needles

[RABBITFISH]

Spare, I had an analog gauge with the needle dial that I hooked up to the battery and connected the signal wire, (green I think) to it and when I started the motor it showed my motor rpm, although a bit high, I suspect because it was meant for an auto, it was steady and showed any increase or decrease in rpm corresponding to the throttle operation. The digital tach worked fine one day, and has for the last 10+ years, and then one day, wtf! It was after the boat sat idle for a few weeks, and was noticed right when I started the motor. Do these things just up and go goofy all at once or do they die a slow death. I was thinking about taking it out the dash and just hooking the power to the battery and connecting the signal wire to make sure of the tach or the wires. What are your thoughts..

[spareparts]

yes, I see them go bad time to time, actually I see all kinds of gauges go bad, teh differnce is most of them don't cost $300. BTW, if any of ya'll are running smart craft, the earlier gauges are no longer being made, you have to replace them with the newer style, the fun begines when you figure out hte newer gauges won't work with your old computer, so if you want the newer gauges to work, you have to buy a new computer($2000+), nothing like planned obsolecense