Disconnecting battery while motor is running

[GraAlaMat77]

Quoted from boatpartstore.com
"Alternator

The alternator is obviously for charging the battery during operation. Alternators come in different capacities, and are rated by amp output. If replacing an alternator, make sure that you replace with same amp rating. A very simply way to test an alternator, is to disconnect the positive battery cable while motor is running. If motor dies, the alternator is bad plain and simple."


We did this today to check to see if the alternator was running. The boat continued to run after we did this. Is anything messed up?

[AquaMarineNJ]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GraAlaMat77 &raquo;</TD></TR><TR><TD CLASS="quote">Quoted from boatpartstore.com
"Alternator
A very simply way to test an alternator, is to disconnect the positive battery cable while motor is running. If motor dies, the alternator is bad plain and simple."


We did this today to check to see if the alternator was running. The boat continued to run after we did this. Is anything messed up?</TD></TR></TABLE>

Not a very good idea, you can burn out the regulator in the alternator that way. Test it another way. Use a volt meter at least.

[GraAlaMat77]

the motor continued to run after we disconnected it, so i guess the alternator was working, even though the voltmeter wasnt registering.

[CA Ken]

Safest & easiest test is to check the battery voltage with a meter when the motor is off. Should be close to 12V DC. Start it up and you should see that voltage at the battery to come up around 13.5V DC. If you see that, the charging circuit is working.

As stated earlier doing it the other way may fry a regulator. That test may not be telling you what you want to know.

What problem are you having with it?

[AB]

The voltage spikes created by doing that can damage the very sensitive components in todays outboards and automobiles. It used to be accepted practice, but in today's world a voltmeter is a must. I can't count the number of high-$$ ecms I've replaced in customers cars after they tried to do this to test their cars alternator.

[GraAlaMat77]

went out today after charging the battery tonight, burned about 30 gallons of fuel, multiple stops (30+ crankups), lights, two grraphs, two livewells. At the end of the day the battery had a charge of 12.6 volts. I have an extra cranking battery, so I guess Im gonna just let it go and see how it turns out and do sumthin about it if a persistent problem arises.