Floating tachometer?

Alright, left gps on in boat so I killed battery.( I know dummy, right!) Charged up battery for an hour and was able to get boat to start right up. So started boat on a set of ears and all was well until I throttled back down after a moment of two and noticed the tachometer was not coming back down. It stayed up around 2000-2200 rpms for about almost a minute and ever so slowly came back down close to 1100 rpm. I know the the engine was running at a lower rpm than that just from experience with the boat motor. Anyway, the engine is a 1988 470 with all the upgrades (Pertronix,alternator,high output coil, etc.) Tach is a Faria, and has worked flawlessly all season. Also, tach is only one season old. Only 150 hours on boat. What would cause this condition? Did not get a chance to get up underneath dash yet. Hoping it is a loose wire or something easy. Yeah right! lol Any and all advice would be greatly appreciated. Thank you, Tom

Does it drop to zero w/key on and engine off? If it won't drop to zero the tach is bad. Faria will replace it for a nomina fee.

+1. Even new tachs go bad. Check your wiring, and if you don't find an issue, try this before giving up the tach; depending on the model, it will have dip switches or a miniature rotary selector switch that you set to match the number of cylinders. Flip the switches up and down or rotate the rotary switch back and forth several times. The internal contacts corrode sometimes. Ensure you return the switches back to the propper settings, and recheck.

Thanks WoodieMan for the heads up! To be honest, I did not even look to see if the tach goes to zero when key switch is at the run position. I will check it out tomorrow up at my shop. And yes, it has the selectors for different engine types and I will switch it back and forth a few times to maybe help it get a better contact. I am thinking that the tach is returning to zero but will recheck to make sure. Hopefully, that might get it to work again.

thanks for all your help, Tom

I got it WoodieMan! Yes! Anyways, finally got a chance to get under the dashboard and did what you said with the keyswitch. It went right to zero with key on run position. I then moved the switch back and forth and could see and hear corrosion through an access slot at bottom of gauge while I turned it back and forth. I also sprayed a little shot of PB Blaster in the whole where the little brass arm makes contact with the housing. It is now working great again. I guess I must have splashed some saltwater on the backside of dash when I was throwing buckets of water on deck while fishing. Don't have room for a freshwater washdown and don't need anymore weight so I use a bucket when the deck starts getting nasty with bait and fish blood.lol The kids kind of slop the bait around if you know what I mean but it is still worth it to get them out there with me. I love being out on the water! Maybe get one or two striper trips down to Cape May New Jersey before I winterize. Thanks again, Tom

Thank you also guyjg for the info. on the Faria gauges. They are good gauges and it is nice to know some companies still stand behind their products. I am happy with the gauges and they look awesome in the dashboard. Good to know! thanks again,Tom

That's great Tom, but you know that if it's corroded in there, it's probably just a matter of time before the fault returns and you have to do it again. You can keep doing this in future until this fix doesn't correct anymore, or contact Faria now, check thier options for replacement and ensure water doesn't get there again. Glad you fixed her up!

...sprayed a little shot of PB Blaster in the whole where the little brass arm makes contact with the housing. It is now working great again.

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You have to love that PB Blaster. They also make a good fuel injection cleaner. I think Faria makes one of the finest gauges on the market. On my last I/O I replaced 8 old gauges w/new Faria gauges. I bought them all from a wholesale dealer for $200; the dealer has since raised his pricing to retail. I changed the white incandescent gauge lamps w/light blue LED lamps. It got rid of the windshield glare and cut down on amp draw from the battery.