'95 merc 150 charging system

[bware-]

I have a '95 150 xri that seems to be not charging as good as it used to.
It seems to have some output, but not like is used to. Could this be the stator or one of the voltage regulators? I have no idea how to diag???

 

[j_martin]

Re: '95 merc 150 charging system

The 2 regulator system is indeed 2 seperate systems. If it's working, the battery voltage should be somewhere between 13 and 14 volts when the engine is running, maybe a little over idle. This, of course, assumes that the battery is good.

You can disconnect the 2 yellow wires to either regulator, and if there is no change (drop) in the voltage, you found eithere a bad stator or regulator. Don't try to unplug them on a running engine, they bite like a crocodile.

You can also move the tachometer wire to the other regulator. Usually (not always) if the regulator fails, it will also fail to drive the tach. The tach should run equally well off either regulator.

Open circuit, the stator will put out anywhere from 20 to about 100 volts at WOT. Don't try to run the output of the regulators without a load. You can, however, connect each to a different battery as long as both negative terminals goe to engine ground. Many bass boats are set up this way.

The mercury regulators commonly fail. The aftermarket ones available (I believe here at I-boats) are better.

hope it helps
John

 

[Texasmark]

Re: '95 merc 150 charging system

That engine has 40 amps of battery recharge capacity. The rect/regulators are only rated at 20A so it takes 2. J has the troubleshooting technique nailed and it may put out more than 14v....like 14.5 or 14.75. A dead charger module would be more like 13 or less. 1000 rpm's is fast enough to get your answer. Make your voltage measurements at the battery terminals where you don't have to worry about any over voltage.

If both regls put out good voltage maybe it's time to clean up your connections...clean, bright and tight.

Totally agree on don't disconnect things with the engine running.

On son's newly purchased boat the tach wasn't working properly. We switched rect/regl modules (gray wire) like J said and the tach still didn't work properly. A new tach solved our problem, but it's a known fact that a bad rect/regl module CAN cause tach problems.

HTH

Mark

 

[bware-]

Re: '95 merc 150 charging system

thanks J & M for the help. using your diag methods I found the lower regulator faulty. i picked one up this afternoon, will install tomorrow. i'll let you know how it goes...
Brian

 

[Texasmark]

Re: '95 merc 150 charging system

Great!

 

[bware-]

Re: '95 merc 150 charging system

Yep! installed that new regulator today & fired her up, now I've got 13v at idle & 14.2 at 1300rpm. Thanks for the help! My batteries & I are a lot happier now...
Brian