Tach Question on new build... where to start looking?

[cmb1998]

I have a rebuilt 2002 carbed 2.5L 200HP I put in the water for the first time this morning. Engine was new top to bottom. New CDI Stator / Trigger. New voltage regulator, although i used a cheap china one.

Fired the engine up and ran great. First time i went to run up to 2K RPM's I noticed the tach wasn't moving. It just sits at about 1K and bounces quite a bit (you can tell the engine isn't bouncing around as much as the tach indicates). Shut the motor down and disconnected the grey wire from the voltage regulator, plugged back in and fired up. Throttled up to ~2K, tach starts to work then immediately does the same thing. Faster i go, the slower the bounce. Engine runs great otherwise. All the rest of my electronics seem to work fine.

Also the voltage is running at 14.4. Is that too high?

Tach worked fine when I pulled the other motor out ~2 weeks ago.

Any ideas where to start looking? Could it be the voltage regulator?

Thanks,

Chris

[FORBESAUTO]

Try swapping the grey wire to other regulator and see if still does it. If it does it's tach or wiring problem. If it does not swap yellow wires from stator between the two regulators and see if it's still ok or starts back doing it. If starts back it's stator, if not it's the regulator. (If you can swap the stator wires on the cdm set up, for the life of me can't remember if lengths will let ya)

[Dave Strong]

If the tach is working with the grey wire disconnected you have a harness issue.

Dave

[cmb1998]

If the tach is working with the grey wire disconnected you have a harness issue.

Dave

Thank you both. Disconnected the grey wire and tach stopped working. Pulled the voltage regulator off the other motor and replaced the new one, and the issues appears to be resolved (at least on the trailer). I'll go dump the boat in the river once the rain stops. Thank you for the help.

Does someone make a better voltage regulator?

[Dave Strong]

Mercury has an updated regulator, expensive but replaced both on my Pro Max fee years ago and work great.

Dave

[cmb1998]

Mercury has an updated regulator, expensive but replaced both on my Pro Max fee years ago and work great.

Dave

Would you by any chance have the part number for the new one? Just want to make sure i get the right one?

[Dave Strong]

883071A 1 these are fused and must change wiring slightly. Instructions come in the box.


Dave

[WillySteve]

Don't forget to switch the little cylinder dial on the back of the tach back and forth 15-20 times and then put it back where it started!
Those contacts get dirty on a regular basis and will make the tach do stupid things!!!