Mercury 150 v6 tach reading drops to zero,

[mckinneyra]

I have an intermitting tachometer. It may show 600rpm at idle in the yard, then drop to zero, yet engine rps sound like there is no change. When I rev up the engine a bit, engine sounds fine, but tach stays at zero. What should I look for on the "gray" wire from the Mercury 150 hp engine.

 

[BIGFLAT]

When I had these symptions, my voltage regulators were bad. Its a simlpe job, as the wires are color coded and the connections are arranged so that one hooks them up correctly. I got mine from this site and saved a bunch...BF

 

[guyjg]

Try WD-40 on the tach setup switches and then exercize them back and forth several times. Corrosion can set in and interrupt electrical signals. If after the WD-40 cleanup doesn't work test the DC voltage output w/a DVM...you should see 12.5 vdc at idle to 14.8 vdc at 1500 RPM depending upon the battery charge condition. If that is good switch the DVM to AC volts and check the battery terminals. There should be no more than 0.01 VAC. If there is then the diode- rectifier/regulator is dying as BIGFLAT said.

 

[faztbullet]

What year engine as it could a couple of types of rectifiers with and with regulators...

 

[mckinneyra]

The engine is a 1989. All the electrical components on the engine were replaced at the same time (for another problem) and it didn't help the tach still being intermittant.

 

[fastjeff]

You might simply have a bad tach. Had to replace mine last year; it did a similar thing.

Jeff

 

[BIGFLAT]

The tach in my boat is a '88 model. It stilll works. Before I would start changing out stuff, I would do a voltage test like guyjg suggested above. If you don't have a digital volt meter, I would go buy one. It is a very handy diagnostic tool...BF