Tachometer fault on 1996 90HP Johnson

" The tachometer on my boat wo

" The tachometer on my boat works OK at idling, but when it gets to about 1200rpm it cuts out. I have tried a replacement tachometer but it still did the same thing.
The battery is still getting charged OK. I had a look at the regulator and it has a red wire connected to the main positive which is charging at 2 amps, but there is also a grey wire and a purple wire that go into a plug which disappears into the loom. When the tachometer is functioning I am getting between 4 & 6 volts across these two wires, but only 2 volts when it stops.
I presume this means the regulator is faulty.
Any advice would be appreciated "

"Rock.... Trying a replacement

"Rock.... Trying a replacement tachometer as you did is the fastest way to diagnose that problem, and you are correct that in all probability, the problem is with the voltage regulator/rectifier assy. There is a work around technique to bypass the regulator assembly simply to get your tach working but I don't recommend it due to the fact that the regulator (if faulty) will fail completely, leaving you with a dead battery, and also cause voltages to back up in the stator assy (under the flywheel) which will cause a stator melt down, plus the fact that eventually the regulator will heat up to a point whereas it will actually catch on fire. I'm assuming that what you have is the "Water Cooled" type regulator that sits atop the block (crankcase) just to the rear of the flywheel. However, if you want to simply try the alternative tach hookup, locate the gray wire from the engine harness that attaches to the other gray wire leading from the regulator. Remove the engine harness gray wire (the one that leads up to your tach) and attach it to the Yellow/gray wire that leads from the stator. The stator sends out a six (6) pulse signal that will operate the tach.... but heed the above warning. NOTE... If you prefer (and I would), you may do away with that expensive regulator and instead install the other type rectifier (the small one) OMC part #583408 that has a list of about $40.00 which will charge your batter just fine, and will also operate your tachometer. It attaches to the starboard (right) side of your block. Keep me informed.

Joe "

I have a similar problem....t

I have a similar problem....tach quits at 1800....then voltage shoots way up..16 volts

Any ideas

Steve