On my Formula 292 fastech I am replacing my 2 tachs.

Port tach had one gray-singnal-wire on S terminal, and one purple wire on ignition terminal.

Starboard tach had two gray-signal-wires on the S terminal and one purple wier on ignition terminal.

wonder why?

I only have one volt meter so I am guessing and only guessing that the starboard tach could be sharing the gray wire with the volt meter if it originates from the alternator......

confusing and the dam wire bundles are so neat and zip tied I really dont want to cut it all apart and pull and search, hopefully one of you guys may beable to help.

Thanks,

LC

If it worked correctly that way and you had no electrical issues, hook it back up the same way......

Can't go wrong with that.....

Not sure why one tach has two gray wires. Has nothing to do with volt meter unless they have the gray and purple wires swapped. Normaly a tach has a purple wire (ignition or power) a gray (sender) a ground and a blue for a light. Usually the gray comes from the distributor or your ignition system on one engine only. Your gauges for each motor should be separate from each other and work off each key switch. Only one power wire comes in to each side usually purple and it jumps from gauge to gauge feeding them all power. Do your tachs work currently?

Maybe the second gray wire on the starboard tach goes on to feed some other device? Your boat should have come with a complete wiring diagram book (3-ring binder). All Formulas are supplied with extensive documentation from the factory. If not, contact the TAG group at Formula, and they can email you the page that you need.

Do you have a sync gauge?

Ok..

Wiring diagrams in my om is for a 312, Formula emailed the 292 diagrams today.

Tachs worked. The starboard one with two grays failed after it had fogged up. Went to max rpm and would work backwards for example went to 8k rpms and would drop to 6k rpms when I was at 2k rpms.

I agree no reason for two grays. Maybe one failed and they pulled another...???

I would imagine that if they pulled another they would have disconnected the bad one for fear it could ground out. And if they went through the effort to pull another, they would have gotten rid of the first anyway.

Possibly it could be connected to an over-rev limiter, sync gauge or hour meter????

hour meter is/was built into the gauge. Now I have a boat with zero hours on the gauge... LOL.

No sync, rev limiter is built into the ing on the motors.... I guess I can just isolate them one at a time and see which one works, or just hook them both up. Funny that this is the tach that failed, wonder if it was a bad conductor replaced and a ****ty tech left the old connected it found ground and thats what failed.

Can I ohm them to ground w/0 risk of damaging the engines computer?



LC

Ok, I think I have it figured out. Formula as an option put the capts call exhaust on a switch to open if rpm went above 3k. I don't have capts call so one of the wires is not needed..... Hope I is right with this assumption. I am just gonna hook it up like it was.