Merc 150 HP XR6 Tach Issue (Regulator)

[exciterfan]

Hello,

The tach on my boat just quit. It was intermitent on one weekend then it died the next weekend.

After doing some investigation I realized that this motor has dual voltage regulators which also provide the tach signal. I have been able to verify that switching the tach lead to the other regulator solves the tach problem. My question is whether this means the voltage regulator needs replacing or not? Can the tach circuit fail and the regulator still function properly?

I know that I can measue the battery voltage while the engine is running to determine if the system is charging, but how do I isolate one regulator or the other? Can you disconnect the yellow input leads to the regualtor and/or the output leads to isolate the good regulator to see if the other one is still working or not. Is it okay to run the system with only one voltage regulator for testing purposes??

I haven't done all of the static resistance measurements tests yet but plan to perform those tonight.


If the tach hadn't failed, I would not have suspected I had any charging system issue.

Suggestions appreciated

Thanks

 

[Chris1956]

Re: Merc 150 HP XR6 Tach Issue (Regulator)

That is a 40A charging system. I believe you can disconnect the yellow wires on the "good"VR and check to see if the "bad" VR will still charge.

BTW - you might expect the other VR to fail shortly. Do you see any burn marks on the "Bad" VR circuit board? It should be visable thru the potting.

 

[exciterfan]

Re: Merc 150 HP XR6 Tach Issue (Regulator)

Thanks Chris. I haven't taken the regulator out yet so I haven't done a full inspection. I wish I could get a hold of the internal schematic of the regulator (I'm an electrical engineer). The regulator and tach circuitry may be independent.

I did test the stator last night and it passed all continuity tests. I also thought I should be able to unplug the inputs to the good regualtor and see if the bad one is still regulating the voltage okay. If it is then I guess I can leave it installed.

I did order a new replacement regulator which supposedly also has a "new additional ground wire" so maybe I should just swap it out.

 

[Chris1956]

Re: Merc 150 HP XR6 Tach Issue (Regulator)

well, if the "bad" VR still charges, swap the tach signal over to the "good" VR and you are good to go. Just so you know, the tach runs off stator pulses. You can also connect the tach to any yellow stator wire and it will work.

 

[Chris1956]

Re: Merc 150 HP XR6 Tach Issue (Regulator)

I also think there would be no way to fix the VR, since the potting material is likely epoxy, and would be hard to remove.

 

[exciterfan]

Re: Merc 150 HP XR6 Tach Issue (Regulator)

I agree, that potting resin is nasty to remove. I was more interested in the design.

I'll check to see if the regulator is still regulating.

I wasn't aware that I could actually just connect it to the stator. I thought the gray tach signal was a half or full wave recified signal??? On my 90 HP merc the signal comes off one of the diodes in the rectifier which should make it a 1/2 wave rectified signal.

I appreciate your input.

Len

 

[Chris1956]

Re: Merc 150 HP XR6 Tach Issue (Regulator)

Len, Usually the tach sender is one of the AC wires from the stator. It therefore sounds like your 90HP motor is miswired. You might check a skematic at maxrules web site.