Tachometer not working

[Andice]

My family has a 2008 Mercury 50hp ELPTO 3cyl 2-stroke on our SunTracker 20 foot pontoon. The tachometer has stopped working. Since the engine appears to be running normal and producing positive voltage recorded via voltage gauge and battery is not loosing charge, I assumed the tachometer had gone bad and voltage regulator was still good.

I replaced the tachometer. However the tachometer is still not working. I then replaced the voltage regulator, 883072T six wire, and the new and old tachometer are still not working. I made sure I had continuity from grey wire (Sender wire)coming out of Voltage regulator ON MOTOR to grey wire on back of Tach gauge: Got continuity on wire from motor to gauge so grey wire is not broken between console and motor. I then checked “Ground wire” continuity on back of Tach to ground on fuse box, got continuity so have good ground. I then checked voltage on “IGN wire” on back of Tach to “Ground” on gauge with key on, got 12+ volts. As stated earlier, volt meter gauge ON DASH is showing 14 volts with engine revved and 12+ at idle. So it appears stator is producing AC volts and Rect/Reg is changing volts to DC …True? Just FYI, both tach's are set/calibrated to 6P on back of tach. I know I am missing something in my trouble shooting. I am hoping one of you guys can offer me some additional items to check. Not sure where to go from here. Thank you for the help.

 

[wrench 3]

Check the gray wire to see if it's shorted to ground or power.
Double check all your connections.

 

[gm280]

Take which ever tach you have at hand, and connect it up at the engine with the gray wire to the console removed. See if it works there. If so, you have a wiring issue regardless what you are seeing doing continuity. The tach should work at the engine... JMHO

 

[Andice]

Thank you Wrench 3 and gm280 for your responses.

I was able to talk to a boat mechanic last night. He told me to make a jumper wire and connect it to one of the yellow wires coming out of the voltage regulator and attach it to the grey wire going to the voltage regulator. He told me that if I get a reading on the tachometer, which I did, that the grey wire within the new voltage regulator is defective. So it appears that the new voltage regulator is working fine except for the grey tachometer wire coming from the new voltage regulator. After testing new and old tachometer, it appears that both the voltage regulator and tachometer went out at or near the same time. So I have contacted the seller/manufacturer of the voltage regulator and they are sending me a new one. I just never thought that the new regulator would have been defective.

Anyway, I am hoping the new regulator will resolve my current issue which appears it will. I wanted to respond so that others will know that although the regulator is apparently producing positive DC voltage to the battery, the grey wire can or could still be defective, even with a new regulator. I hope the test I performed jumping the yellow to grey wire was helpful to the forum, it was for me.

 

[GA_Boater]

The gray wire out of the regulator is simply connected internally to one of the yellow stator connections.

That's why the tach worked when connected to one of the yellow stator wires.

It sounds like when the original regulator failed, it spiked the gray tach wire and torched the old tach.

The replacement regulator should do the trick and charges the battery along with running the tach the way it's supposed to work..