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Starboard alternator over charged

S

slow cruiser

Regular Contributor
First time out since launch the starboard alternator was over charging @ 16+ volts. Returned to the dock checked all connections were tight, gauge was accurate. Restarted it several times, same problem. On the fourth start the charging rate was correct and for a couple more starts. I have a Charles in line digital charger. The batteries were fully charged (12.45 volts) when this happened. The charge rate was correct at idle but jumped to 16+ at 1,000 rpm.
Engines are 2001 8.1 liter with 500 hours and 100 amp alternators.
What could cause this, I don't want to replace the alternator at $800 nor do I want it to happen at an inopportune time.
 
not being connected to the battery, causing the alt to run wild not seeing the "12v sense"
bad internal regulator
100A is overkill anyway
Being a twin are you sure you actually have independant motors? sometimes both outputs are wired to a common isolator
 
Bad regulator would be my first guess....

$800 - are you serious?? The MSRP I'm seeing is under $300 (crusader part) and the aftermarket units go for quite a bit less.....labor can't be that brutal - even under a fixed deck....
 
Bt Doctur said:
not being connected to the battery, causing the alt to run wild not seeing the "12v sense"
bad internal regulator
100A is overkill anyway
Being a twin are you sure you actually have independant motors? sometimes both outputs are wired to a common isolator
Click to expand...

If the regulator is bad would it work and then not work? Has functioned well until now.
100 amp, came with the boat.
Motors are not connected except perhaps through the charger, but the port was charging properly.
 
Last edited:
makomark said:
Bad regulator would be my first guess....

$800 - are you serious?? The MSRP I'm seeing is under $300 (crusader part) and the aftermarket units go for quite a bit less.....labor can't be that brutal - even under a fixed deck....
Click to expand...
The part number is RA097008, where is it listed for under $300, please.
 
the number I got was RA097007, the 70 amp alternator. They list for ~ $275. Aftermarket ones are about half of that. And PCM buys them, they don't have unique source that makes them unique. As long as they are 'sealed' (for marine safety), they typically have a lebel with the SAE number on them.

Like the Doctur said, 100 amps is way more than adequate.....I'd use the 70 amp one. If you are convinced you need the 100amp unit, I'd bet any decent alternator shop could upgrade a 70 amp unit and still save your hundreds....
 
makomark said:
the number I got was RA097007, the 70 amp alternator. They list for ~ $275. Aftermarket ones are about half of that. And PCM buys them, they don't have unique source that makes them unique. As long as they are 'sealed' (for marine safety), they typically have a lebel with the SAE number on them.

Like the Doctur said, 100 amps is way more than adequate.....I'd use the 70 amp one. If you are convinced you need the 100amp unit, I'd bet any decent alternator shop could upgrade a 70 amp unit and still save your hundreds....
Click to expand...

Thanks Mark, the 70 amp are common and less than $120. Would it be just a 'plug and play' or would I need to make any adjustments? As I said the 100 amps came with the boat, I have no idea why the original owner ordered them, paranoia perhaps.
 
Most all marine alternators cut back on the charge rate rather quickly.
I agree....... 100 amp is over-kill.

I'd also be willing to bet that the OEM harness is just barely heavy enough to effectively handle a continuous 100 amp charge rate.
 
slow cruiser:

From what I gather from the later parts diagrams, I'd say the 70 AMP doesn't interchange with the 100AMP alternator without a lot of extra work & parts swaps. it also appears that the 100 amp unit is from Balmer and has an internal regulator. I'd think that getting your existing unit overhauled would be the best course.....

overall, Balmer has had a good reputation.....some of their newer products have left some people with a non-positive attitude.....
 
makomark said:
slow cruiser:

From what I gather from the later parts diagrams, I'd say the 70 AMP doesn't interchange with the 100AMP alternator without a lot of extra work & parts swaps. it also appears that the 100 amp unit is from Balmer and has an internal regulator. I'd think that getting your existing unit overhauled would be the best course.....

overall, Balmer has had a good reputation.....some of their newer products have left some people with a non-positive attitude.....
Click to expand...

That's what I thought, not a simple replacement. There must be a reason for the 'substantial' price difference.
I'm going to check it again this weekend and look into having a local shop rebuilt it.
 
slow cruiser said:
That's what I thought, not a simple replacement. There must be a reason for the 'substantial' price difference.
I'm going to check it again this weekend and look into having a local shop rebuilt it.
Click to expand...

I found the wiring/installation diagram from Balmar, it was a loose wire. Check the simple things first, I had over looked this the first time.
 
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