Alternator

[enablers2]

I have a 2002 340 Sundancer and have recently had to replace both alternators. The starboard alternator was replaced under warranty by the dealer in Sept 2008 and just went out again...Merc alternator 863077T was installed. As far as I can tell this was the correct alternator... Anyone having alternator issues?? DB electrical (on line)has new aftermarket replacement for 1/3 of the price ($114). Any thoughts? Why would an alternator crap out after 1 yr. Boat wasn't run that often this past year.

Help
Rich
enablers2

 

[njmorrell]

I have a couple of aftermarket Mando alternators on the engines of my boat, they are several years old and work fine.

Most of the time people replace alternators when if fact the problem is elsewhere, they should last for years. I guess incorrect or faulty wiring could cause failures.

Rgds Nick.

 

[jason78]

I have a 2002 340 Sundancer and have recently had to replace both alternators. The starboard alternator was replaced under warranty by the dealer in Sept 2008 and just went out again...Merc alternator 863077T was installed. As far as I can tell this was the correct alternator... Anyone having alternator issues?? DB electrical (on line)has new aftermarket replacement for 1/3 of the price ($114). Any thoughts? Why would an alternator crap out after 1 yr. Boat wasn't run that often this past year.

Help
Rich
enablers2

Could be a bad battery??

 

[jcoll]

I agree - batteries can be the cause. Have them load tested if that's possible for you. I'll assume you maintain them properly, fluid level correct and terminals clean and tight. If the batteries are good, you need to do voltage drop tests to find the source of resistance in the circuit. Electrical resistance will cause the alternator to overwork and fail prematurly. To do this test all you need is an inexpensive voltmeter. Connect the leads of the voltmeter ( + and -) to either end of 1 side of the circuit -i.e. 1 lead on the positive battery terminal and 1 lead on the positive output terminal on the back of the alternator. With the engine running and as much 12v electrical load (lights etc.) you can put on the circuit, you looking for a reading of .2 volts or less (this will depend on how many connections there are between the alternator and the battery) but there should not be more than .5v drop in the circuit. Do the same for the negative side of the circuit - 1 lead on the back case of the alternator and 1 lead on the battery negative terminal. Again you want .2 volts or less. If your readings are substantially higher than this, start looking for corrosion wherever wire connections are or wherever cables are grounded to the block and battery. Remove and clean these connections with sand paper.
Jim

 

[JV II]

Check your battery switches. Turning them off while engine is running can kill the alternator. Losing contact in a faulty switch can do the same thing. Just a thought.