Alternator Not Charging

[zipper]

My 1999 502 mercruiser alternator has went on the fritz. It's not charging.... I've had experiences in the past with GM automotive alternators and it was always the built in regulator that went bad.
Anyone know if these units are similar to the automotive units.
If I need a replacement what would the rating in amps be & where I might find a reasonably priced replacement.
Thanks In Advance

[gcarter]

There's always a bunch of new and rebuilt marine alternators on eBay.
You can do a search on Mercruiser alternators.
It needn't be an exact replacement as the pulley is interchangeable. You'll also have choices on a one wire or three wire units. Output choices are also many. More is usually better.
I personally don't care for one wire alternators as they are self exciting and are "dead" at idle. They have to be revved up a bit to get them to charge. A high output three wire alternator can put out a pretty good charge at idle.

[zipper]

Mr. Carter... Thank you very much for the very speedy reply.
One wire or three wire ? Wouldn't it have to be replaced with the same that came off of it. I guess I haven't looked at mine yet to see how many wires mine is... didn't know there was a difference.

[gcarter]

Most three wire alternators will have a purple wire that originate from the (+) side of the coil, and a red and purple wire that originates from both the main circuit breaker and the starter slave solenoid. These wires are used to excite the voltage regulator, and a heavy orange wire that actually carries the output current.
A single wire alternator only has the large orange wire (plus a ground wire) and is self exciting, which makes for an easy installation, but it doesn't produce at idle speed. That's what I don't care about as it could reduce your battery capacity if you're idling for a long period of time.
It's not necessary to have an exact replacement as Mercruiser uses alternators from several MFGR's.
When (or if) you shop on line, you'll notice they come in various outputs, like 50 Amps, or even over 100 Amps, the choice is yours. It's nice to be able to recharge the battery quickly if it's down.

[Tidbart]

The short answer to your question about the reg, is yes, it can be replaced. It is different than the GM regs that I remember that had a 2 terminals and were internal to the case. The Mando's reg is on the back of the unit and also comes with the brushes and spring. You would replace them together. About $90 bucks for the part.
# should be 811883T but you would need to verify by your serial number.

Replacement looks pretty easy, only a couple of mounting screws. You will need a small wire or drill bit to hold back the brushes during install similar to the old GM ones.

BTW, the stock alt is a 65 amp unit.

If you don't have the Merc manual #23, look for one on ebay. They are worth every penny. You can buy a disc even cheaper, or you may even find a download online.

If you want the alt section, pm me your email address and I will send you that section. It has the compete test and rebuild procedures for that alternator.

Or, as George said, you can just buy another one.

Good luck, Bob

[gcarter]

Yeah, here's some examples of new alternators on eBay...
First, a one wire, 105 Amp;

http://www.ebay.com/itm/NEW-105-Amp-...13d0f3&vxp=mtr

And a three wire Delco 110 Amp;

http://www.ebay.com/itm/NEW-MERCRUIS...6dd7cd&vxp=mtr

Or a Mando three wire;

http://www.ebay.com/itm/100-NEW-MERC...95cf6a&vxp=mtr

At these prices for a new alternator, why would anyone bother rebuilding one?

[Conquistador_del_mar]

Yeah, here's some examples of new alternators on eBay...
First, a one wire, 105 Amp;

http://www.ebay.com/itm/NEW-105-Amp-...13d0f3&vxp=mtr

And a three wire Delco 110 Amp;

http://www.ebay.com/itm/NEW-MERCRUIS...6dd7cd&vxp=mtr

Or a Mando three wire;

http://www.ebay.com/itm/100-NEW-MERC...95cf6a&vxp=mtr

At these prices for a new alternator, why would anyone bother rebuilding one?

Wow! I recently had the alternators and starters rebuilt for a Cigarette project and paid more to have the alternators rebuilt than I could have bought new ones for. I had no idea they were so cheap!

[joseph m. hahnl]

Chinola. I did the Mando parts replacement route when I got the Minx in 2005 worked great 1 yr The 2nd year no so .Replaced with a Delco Remy in 2007 for a $100 and change. Still running on the Phenix 400 2013

[zipper]

If you want the alt section, pm me your email address and I will send you that section. It has the compete test and rebuild procedures for that alternator.

Good luck, Bob

Bob
Would really appreciate you emailing that section. I think I may buy a replacement but then in my spare time rebuild the malfunctioning one.
I will PM you my email address
Thank You very Much

[zipper]

For all the responses on my broken alternator.... Thank You all very much

[gcarter]

Zipper, I guess I should clarify one point, if a one wire alternator is chosen, the existing purple, and red and purple wires aren't used. They can be insulated w/tape or something else.

[tmdog]

Lets clarify another point. One wire alt.once excited do charge at idle speed. My choice is one wire for simplicity.