Tach trouble..Help, I'm running out of options...

[fatboy1972]

My tach is no longer reading but the lights in the guage are working. Boat is a 1978 15' Whaler witth a 1987 70hp Yamaha.
I replaced the recitifer and still no change. Next, I replaced the tach with a brand new tach.
Upon install of the new tach, it still is not reading. My electrician isolated all of the other light & oil wires, and that leaves a black, green & yellow. Here's the interesting part, only AFTER we unplug the yellow wire, does the tach read, for about 1-2 seconds, then it stops reading. My electrician is baffled. Any suggestions, since I have changed the rectifier & the tach? I'm about to give up!!!!!!

By the way, I did purchase the recitifer and the tach from this company, so I would appreciate some assistance with this. This is my second posting, on the same topic, and never received the first response!!!!!!!

[Finisher]

Not sure what you mean by not reading, no tach info or no numbers or wrong rpm? Just to make sure black is ground yellow is key on green is the tach signal and blue is the light. start there
p.s. I don't work here just lending some advise

[fatboy1972]

Tach trouble

This is actually an analog tach and the dial moves for about 1-2 seconds, immediately after the yellow wire is disconnected.

[dngharvey]

tach

Recently added the same tach to my '88 70 hp. Would not work till light was hooked up. Ended up taking it to a dealer who went thru a number of manuals to find this out. The oil lights, however, do not work as there are not enough wires from the engine on the older models.

[throrope]

Sounds like a bad or corroded connection. They can pass enough electricity to fool you and then resistance creates heat that then completely losses connectivity. Start with a OEM wiring diagram and find the first connector at the outboard. Disconnect, clean and reconnect with some dielectric grease, move to the next until you find one or more in bad shape or get to the tach and try again.

[jb123]

have you tested the harness

[hewesbayfisher90hp]

Not quick

This sight seems quick to sell you the part, but very slow on advice - wish I could help you more. I have had posts up for weeks with no response - seems when you are spending thousands of dollars it would be worth a few minutes - seconds of their time.