Which alternator for Merc BBC?
#1
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Kind of a newbie question but as I cannot return anything I want to be sure before I order.
Which is the standard alternator for a Mercruiser Gen IV Big Block, which OEM part number?
And, why my alternator has 4 cables but only 3 connected? (and works fine)
Any recommendation which to order? Looking for one with some chrome.


Which is the standard alternator for a Mercruiser Gen IV Big Block, which OEM part number?
And, why my alternator has 4 cables but only 3 connected? (and works fine)
Any recommendation which to order? Looking for one with some chrome.


#2



I went with this company. No idea if the have anything chromed. But it works great. Direct bolt on and plug in.
I'd have to think you've got another wire hangout ng loose in there someplace to plug into the one that is not currently used.
#3
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You have an old mando Alternator but I can't say what the differences were off hand (AMP output or mounting bolt pattern)
Do you have the engine serial number (riveted on a small metal plate behind the starter mount of the engine on the flywheel housing - or more modern engines are on the spark arrestor cover)?
If yes, you can use a website like the following to find the exact alternator that was on you engine and work from there...
https://www.mercruiserparts.com/v-8-inboard-engines
Do you have the engine serial number (riveted on a small metal plate behind the starter mount of the engine on the flywheel housing - or more modern engines are on the spark arrestor cover)?
If yes, you can use a website like the following to find the exact alternator that was on you engine and work from there...
https://www.mercruiserparts.com/v-8-inboard-engines
Last edited by speicher lane; 01-24-2021 at 09:19 AM.
#4
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oconnor marine (01-25-2021)
#6
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iTrader: (1)

You have Mando ALT p/n 817119A4
alternate p/n's
One listed above
Wilson 90-31-7008
SIERRA 18-5966
MALLORY 9-19101 and many others
The ALT has 4 connections but will work with 3 do to the case is ground.
Its working but don't think its working correctly with it being wired the way it is, but would need to put a meter on the bat when running to verify
Orange - output to stater post (battery)
Purple - excite (turns ALT ON with key)
Red/Purple - Sense lead
Black - case Ground

alternate p/n's
One listed above
Wilson 90-31-7008
SIERRA 18-5966
MALLORY 9-19101 and many others
The ALT has 4 connections but will work with 3 do to the case is ground.
Its working but don't think its working correctly with it being wired the way it is, but would need to put a meter on the bat when running to verify
Orange - output to stater post (battery)
Purple - excite (turns ALT ON with key)
Red/Purple - Sense lead
Black - case Ground

The following 2 users liked this post by AllDodge:
musthave1 (01-24-2021), oconnor marine (01-25-2021)
#7
Platinum Member

Thread Starter

You have Mando ALT p/n 817119A4
alternate p/n's
One listed above
Wilson 90-31-7008
SIERRA 18-5966
MALLORY 9-19101 and many others
The ALT has 4 connections but will work with 3 do to the case is ground.
Its working but don't think its working correctly with it being wired the way it is, but would need to put a meter on the bat when running to verify
Orange - output to stater post (battery)
Purple - excite (turns ALT ON with key)
Red/Purple - Sense lead
Black - case Ground
alternate p/n's
One listed above
Wilson 90-31-7008
SIERRA 18-5966
MALLORY 9-19101 and many others
The ALT has 4 connections but will work with 3 do to the case is ground.
Its working but don't think its working correctly with it being wired the way it is, but would need to put a meter on the bat when running to verify
Orange - output to stater post (battery)
Purple - excite (turns ALT ON with key)
Red/Purple - Sense lead
Black - case Ground
Still not completely sure about the cabling. There was not even a fourth cable around to connect the open black cable.
But somehow it’s working, at least it’s charging the battery with 13.3 V output when I run the engine on my test stand.
speicher lane: It’s from an ‘87 Top Gun, maybe the alternator is really 34 years old and was swapped from the original engine to at least two following ones, the last being a 582 Shafiroff without serial number. Which is why I sometimes struggle to find the right parts.
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bigfarmer (01-24-2021)
#9
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AllDodge has you covered for info that you need.
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musthave1 (01-24-2021)
#10
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Thread Starter