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Mercruiser 5.7 alternator replacement

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Cliffs

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I have a 1990 Sea Ray with a 5.7 L, raw water cooled engine, serial number OC759123. I need some help figuring out what alternator I need to purchase. I haven't removed the old alternator yet. Will the old alternator have a number on it that I can reference online for a replacement or is there a better number to use that will tell me which alternator to use? Any help would be appreciated.
 
Good news and Bad news

Bad news, your serial number shows there can be one of 4 Alt's for your motor

Good news, they have all been replaced by 817119A4 it's 55 amp

Use the number to search and find a marine Alt at lower price
 
Cliffs said:
I have a 1990 Sea Ray with a 5.7 L, raw water cooled engine, serial number OC759123. I need some help figuring out what alternator I need to purchase. I haven't removed the old alternator yet. Will the old alternator have a number on it that I can reference online for a replacement or is there a better number to use that will tell me which alternator to use? Any help would be appreciated.
Click to expand...
Where are you located? Look online for places that can rebuild starters & alternators- it's may be possible for them to upgrade the current output- this applies to the Delco brand, not Motorola.

If you're near Milwaukee, I can recommend a place, whether it can be upgraded or just repaired.
 
Rebuild if you can find a local rebuilder, if not look at ARCO Marine's catalog, I have used both their alternators and starters. Not the cheapest but good.
 
AllDodge said:
Good news and Bad news

Bad news, your serial number shows there can be one of 4 Alt's for your motor

Good news, they have all been replaced by 817119A4 it's 55 amp

Use the number to search and find a marine Alt at lower price
Click to expand...
Good information. I only need an oem 55 amp model. Where and/or how did you search to use the engine serial number to get the alternator number? I did a Google search by the alternator number you gave me and there are so many options. I would only use a marine alternator but what is the difference between an automotive alternator and a marine alternator? What is the "Black Scorpion" model that I see reference so much online?
 
jimn said:
Where are you located? Look online for places that can rebuild starters & alternators- it's may be possible for them to upgrade the current output- this applies to the Delco brand, not Motorola.

If you're near Milwaukee, I can recommend a place, whether it can be upgraded or just repaired.
Click to expand...
I'm in Washington state. I have relatives in Milwaukee :) I don't think I need it upgraded, just repaired. It is giving a high pitched squeal that needs to go away. I wonder if a dab of oil would quiet it?? Probably not a permanent fix... I have a local, very good, alternator/starter repair shop, but I assume the repair would be as much as a complete new one.
 
Cliffs said:
Good information. I only need an oem 55 amp model. Where and/or how did you search to use the engine serial number to get the alternator number? I did a Google search by the alternator number you gave me and there are so many options. I would only use a marine alternator but what is the difference between an automotive alternator and a marine alternator? What is the "Black Scorpion" model that I see reference so much online?
Click to expand...
Search mercruiser parts
Once there you can enter the serial number

The black scorpion is a fuel injected motor made by merc
 
Cliffs said:
Good information. I only need an oem 55 amp model. Where and/or how did you search to use the engine serial number to get the alternator number? I did a Google search by the alternator number you gave me and there are so many options. I would only use a marine alternator but what is the difference between an automotive alternator and a marine alternator? What is the "Black Scorpion" model that I see reference so much online?
Click to expand...
 
Cliffs said:
I'm in Washington state. I have relatives in Milwaukee :) I don't think I need it upgraded, just repaired. It is giving a high pitched squeal that needs to go away. I wonder if a dab of oil would quiet it?? Probably not a permanent fix... I have a local, very good, alternator/starter repair shop, but I assume the repair would be as much as a complete new one.
Click to expand...
Are you sure the alternator is making the sound, or could it be from the belt being glazed? I would give the backside of the belt a squirt of water and if the sound stops, change the belt.

I would look into higher current models and compare the price to 55Amp versions- at this point, the difference is far less than before and it makes using accessories easier because the alternator won't be taxed to the same extent.

The current capacity often depends on the belt type, though- V belt capacity is lower than the wider, flat serpentine type.
 
jimn said:
Are you sure the alternator is making the sound, or could it be from the belt being glazed? I would give the backside of the belt a squirt of water and if the sound stops, change the belt.

I would look into higher current models and compare the price to 55Amp versions- at this point, the difference is far less than before and it makes using accessories easier because the alternator won't be taxed to the same extent.

The current capacity often depends on the belt type, though- V belt capacity is lower than the wider, flat serpentine type.
Click to expand...
The belt doesn't look glazed but I like the "squirt of water" suggestion. I don't want to start it now because it's winterized and it will be well below freezing for months to come. This is a V belt alternator.
 
Cliffs said:
I'm in Washington state. I have relatives in Milwaukee :) I don't think I need it upgraded, just repaired. It is giving a high pitched squeal that needs to go away. I wonder if a dab of oil would quiet it?? Probably not a permanent fix... I have a local, very good, alternator/starter repair shop, but I assume the repair would be as much as a complete new one.
Click to expand...
Repair should be far less than a new one
Agree, it could be the bearing or the belt

Suggest remove the belt and grab the pulley then feel if there is any play, does it spin freely and is there any roughness

Look at the belt in the pulley, is the belt below the top edge of the pulley? If so, need another belt
 
Cliffs said:
I found this website, thanks.



Do you know the difference between the two different Mando alternators that they list?
Click to expand...
Only thing I can tell is by the illustrations. What jumps out to me is that the first Mando alternator uses a different type of fan. You should be able to inspect your alternator to tell which of the two types that you have. If that is your objective.
 
Cliffs said:
This website doesn't show alternator for my 1990 Mercruiser 4 BL, Alpha 1 sterndrive
Click to expand...
It shows both Mando alternator part numbers superceding to the same part number non OEM alternator.

The year not being shown is irrelevant.
 
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