Intermittent Tach

[baddjonny]

92-2.5 offshore merc seems to be loosing signal from the regulater as this engine has duel reg's tried the other reg output wire and tach sat there dead soon as I connected it to the orig. top reg it worked fine I know I'm loosing the tach signal at the dash as I connected my fluke dmm on ac to the tach connecter on AC and at around 3000 rpm the voltage would drop from around 4-6 volts down to .05 volts have not tested at the engine side of the harness yet. By the way this intermittent rarely happens at the dock only when the boat is driven over 3000 rpm . It's the port motor of a pair .

PS we tried swaping tachs for a shot in the dark NG .But I don't know why the tach would not work off the bottom regulater tach output.

baddjonny

[vector mike]

Whenever the tach doesn't work it is usually the rectifier.

[baddjonny]

Battery charginging at 14.3 volts at aprox 2000 rpm. This engine uses duel regs/rects I don't know if it will still show a good charge with one bad ???

jon b

[ImbadBob]

Unhook the batteries, take the gray lead from the bad tach and put it on the ground terminal with the ground wire. now lift the lead off the rectifier, get your fluke back out and read resistance ; lead to ground. Wiggle theconnection plug on the starboard side of the motor, have seen problems here. If it's not here just keep shaking wires looking for a momentary increase in resistance. The possibility of a bad tach also exist, Shunting ac signal to ground, could also be stator. Good luck Bob

[stvhelm]

Try swapping the stators between the 2 motors. thats usually an idication of a bad stator. Another thing you can try before getting dirty is swapping the tach wire to the other terimnal on the rectifier. Your tach should read off either yellow wire on the rectifier.