tach problems

[chris0061]

I have a 140 horse evinrude and was doing a tune up and noticed a bad wire on the rectifier, I got a new one, changed all the leads on the cables to the battery. Before I did this my tach would go crazy while on plane, jump from 4500 to 6000 exc exc. And when I turned on the lights it would quit working. After I put the rectifier on the tach quit jumping but bottoms out at 6000 rpms and it still quits working when I turn on the lights. Is this a bad tach or is it coming from the engine? It seemed like it did have more rpm from sound after I put the rectifier in so I didn't run it full throttle to long.

 

[F_R]

Re: tach problems

Sounds to me like you somehow have the tach grounded to a lights wire. Ground it directly to the engine powerhead like it's supposed to be.

 

[chris0061]

Re: tach problems

OK what do I need to do, trace the wires from the tach to the back of the boat and Find the ground and ground it to a bolt on the powerhead that dosent have a ground on it? Thanks, Chris

 

[Silvertip]

Re: tach problems

The tach has a ground wire, +12V when the key is on, send, and light. The only wire that goes to the engine is the send line and even that wire can connect at the control box. Every instrument on your dash (except the speedometer and water pressure gauge (if you have one)) has a ground connection on it. Ground the gauge to any one of those terminals. Likewise, the gauges are all fed +12V from the ignition switch. Connect the +12V line to +12V terminal on any gauge. Same for the light. You apparently have the SEND wire on the tach connected somehow to the light switch. You need to fix that problem first. You do not need to ground the tach all the way back to the engine. In fact you may have a ground-loop, meaning there is a ground issue on the boat. Make sure the battery cables are clean and tight on both ends. The ground wire in the control box harness should be connected to the ground buss at the console. If you have a bad ground up front, current will find a way anyway it can to get back to the battery and that may be through any gauge, causing it to go goofy. Check your light and ground circuits.

 

[chris0061]

Re: tach problems

OK, I got it, I took the dash apart and found the purple wire jumped to the trim gauge and the blue wire jumped to the speed gauge light. I traced the gray wire to the terminal bar on the engine and started tracing the black ground and found it was disconnected. I hooked it back up and everything works great. Thanks for your help here on iboats.