View Full Version : Mercruiser alternator question
Fish Slapper
09-06-2008, 04:22 PM
I think my alternator may be bad, I assume it works just like the alternator on a car, I did not have a hand held volt meter to verify but when the engine is running I lifted the positive cable off the battery and it died immediately, normally this means the alternator is dead correct? do they have fuses on them by chance?
infinity22
09-06-2008, 06:48 PM
I think my alternator may be bad, I assume it works just like the alternator on a car, I did not have a hand held volt meter to verify but when the engine is running I lifted the positive cable off the battery and it died immediately, normally this means the alternator is dead correct? do they have fuses on them by chance?
your alternator is not working!! time to replace it.
fishkisser
09-06-2008, 06:58 PM
No fuses on the alternator ... I would not rely on the pulling the battery terminal test to determine the condition of your alternator ...
Check Battery voltage with a voltmeter with engine off , at idle and at 2000 rpm's or above ...
Voltage should be higher running and maybe a tad higher at 2000 rpm's than at idle if it is higher than 14.5 volts then your regulator is kaput ...
Barney ...:wave:
Fish Slapper
09-07-2008, 11:12 AM
No fuses on the alternator ... I would not rely on the pulling the battery terminal test to determine the condition of your alternator ...
Check Battery voltage with a voltmeter with engine off , at idle and at 2000 rpm's or above ...
Voltage should be higher running and maybe a tad higher at 2000 rpm's than at idle if it is higher than 14.5 volts then your regulator is kaput ...
Barney ...:wave:
Yes I definitely plan to check it with a volt meter first, I actually had a cheap one on the boat but ofcourse it did not work either. I plan to go down to the boat tomorrow afternoon with a new battery and a new volt meter, I looked up the schematic and lifting the cable does not necessarily mean the alternator is bad. I do have a new alternator on stand by just in case.
Many marine alternators need a 12V igniton source to light up. The terminal on the back may be labeled IGN, EXC, or Ignition. The wire is commonly purple or black. With the key off, you should have no voltage there, but have 12V (battery voltage) with the ignition key on. Make sure that wire has not fallen off.
Here's a good diagram to look at: http://www.arcomarine.com/xhtml/Tech%20Marine%20Alternator%20tips.pdf