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Alternator for 310 (2003)

May 2, 2012
233
Catalina 310 Toronto
Since I'm in the process of changing all the batteries and charger I was reading up on the Marine How To website. They mentioned that the Alternator is critical for charging. Wrong one and it can cause problems. Does any of this Talent Pool know what we have on our boats. Mine is a 2003 model. Diesel is M25XPB.

Cheers
2 OLD PIRATES
 
May 20, 2016
2,989
Catalina 36 MK1 94 Everett, WA
I have a 90Amp L&N 8MR on currently and a 105A Compass Marine ready to swap in. This is on a M25 so should work for you. Both are externally regulated. You can’t go wrong supporting the site you’ve hit up for the knowledge.....,,
 
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Likes: Ward H
Oct 22, 2014
15,340
CAL 35 Cruiser moored EVERETT WA
2OP you might give us a picture to reduce our need to SWAG the answer. You may even find a model and serial number on the side of the alternator to give you the exact item. One never knows what a previous owner may have done to or installed on the boat.

As Les has shared you can get a good replacement from MaineSail on the "Marine How To" website.

The "External Regulated" units are identified in the alternator article. It explains the advantages of this system design. Highly encouraged to get the most out of your system charging.
 
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Likes: Ward H
Feb 26, 2004
21,716
Catalina 34 224 Maple Bay, BC, Canada
One never knows what a previous owner may have done to or installed on the boat.
John's right. If, however, it's an OEM, it is most likely a Motorola 51 or 55 A internally regulated unit.
Replacement realities ALWAYS start with "How do you use your boat?"
If you are regularly connected to shorepower, DO NOTHING.
If you want to extend cruises and anchor out without shorepower or solar, consider a higher output eternally regulated alternator and a Balmar MC-614 regulator.
If you have a healthy solar system you may not need the alternator upgrade.
All sorts of combinations here, and generators haven't even been mentioned.
"How do you use your boat?"
Your boat, your choice. :)
 
Nov 18, 2010
2,441
Catalina 310 Hingham, MA
The OEM is a 55 amp Moterola. Conveniently enough it's the same alternator and pulley as many of the Merc cruiser power boats. So you can get a knock off for around $75.

Now go read Mainesail's article on car alternator vs. deep cycle batteries. This happened to us with a bank of 4 GC 6v batteries.

We have been running a Compass Marine Inc. (yes, Mainesail's company) CMI-105-ER 105A alternator through a Balmar MC-614 regulator for about a year. It fits. I had to modify a bolt on the alternator to get it to fit. I wish there was more room under the stairs to roll it out to get more distance from the motor for heat dispersement. But again, no issues in a year, about 200 hours.

Very happy with the quality and finish of the alternator.
 
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Likes: jssailem
Nov 16, 2012
997
Catalina 310, 2000, #31 31 Santa Cruz
John's right. If, however, it's an OEM, it is most likely a Motorola 51 or 55 A internally regulated unit.
Replacement realities ALWAYS start with "How do you use your boat?"
If you are regularly connected to shorepower, DO NOTHING.
If you want to extend cruises and anchor out without shorepower or solar, consider a higher output eternally regulated alternator and a Balmar MC-614 regulator.
If you have a healthy solar system you may not need the alternator upgrade.
All sorts of combinations here, and generators haven't even been mentioned.
"How do you use your boat?"
Your boat, your choice. :)
One drawback of the OEM alternator is that it produces an E03 on our Balmer Smart Gauge now and then. High voltage error. Presumably an external regulator wouldn’t do that.
 

Ward H

.
Nov 7, 2011
3,025
Catalina 30 Mk II Barnegat, NJ
Replacement realities ALWAYS start with "How do you use your boat?"
If you are regularly connected to shorepower, DO NOTHING.
If you want to extend cruises and anchor out without shorepower or solar, consider a higher output eternally regulated alternator and a Balmar MC-614 regulator.
If you have a healthy solar system you may not need the alternator upgrade.
Well said @Stu Jackson.
As @jssailem and @LeslieTroyer said, Maine Sail's www.marinehowto.com website has a lot of good info and he gives great support for items you purchase from him.
 
Feb 6, 1998
11,417
Canadian Sailcraft 36T Casco Bay, ME
Wow guys I had no idea how many CMI/MarineHowTo.com customers could be in one thread. Thanks for the support! Yes, we do specialize in affordable externally and internally regulated alternators that work extremely well on Universal Diesels. Every alternator is custom built, by hand, one at a time right in our shop here in Maine.

We have multiple options in both internal (IR) or external regulation (ER). We have a 72A, 90A and 105A all 8MR frame and also have a 90A Delco based frame designed to drop into where an 8MR or Mando was. The Delco frame unit can even accept a J10 serpentine pulley.

Again guys thanks for the support!
 
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Likes: Ward H
Feb 6, 1998
11,417
Canadian Sailcraft 36T Casco Bay, ME
FWIW the Mando's Westerbeke began using are an inexpensive Korean knock off of the Leece-Neville 8MR's. The "Mando's" linked further above are not actually even Mando's but rather a knock-off of a knock-off. :wink:
 

KZW

.
May 17, 2014
778
Catalina 310 #307 Bluewater Bay, FL
FWIW the Mando's Westerbeke began using are an inexpensive Korean knock off of the Leece-Neville 8MR's. The "Mando's" linked further above are not actually even Mando's but rather a knock-off of a knock-off. :wink:

I have no dispute with anything Maine Sail posts, including the above. I can only say what was on my boat when I bought it 4.5 years ago. In that time the alternator has functioned without issue.
 
Feb 6, 1998
11,417
Canadian Sailcraft 36T Casco Bay, ME
I have no dispute with anything Maine Sail posts, including the above. I can only say what was on my boat when I bought it 4.5 years ago. In that time the alternator has functioned without issue.
Westerbeke uses the actual Korean made Mando, on a few engines, not a Mando knock-off. It is a decent little alternator but still not the quality of a LN. I can't say the same for the non-name Mando copies.
 
Nov 16, 2012
997
Catalina 310, 2000, #31 31 Santa Cruz
Now go read Mainesail's article on car alternator vs. deep cycle batteries. This happened to us with a bank of 4 GC 6v batteries.
Would a Balmer Smart Gauge let you know that the alternator isn’t getting the bank fully charged? The problem would still be there, but you might be more aware of it.

Just wondering. We’re at the dock on AC most of the time (so no issues with keeping the batteries topped up) but if we do take off for an extended trip it would be good to know if there’s an issue.
 
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May 2, 2012
233
Catalina 310 Toronto
So much info. We basically day sail. We have weekend trips usually 4 times a summer (Lake Ontario). Destinations are always plugin at dock. Does this help at all?
Found out that the alternator is a Motorola 51A
Cheers
2 Old Pirates
PS. Here is a new diagram, input is appreciated.
New Setup.jpg
 
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Nov 16, 2012
997
Catalina 310, 2000, #31 31 Santa Cruz
So much info. We basically day sail. We have weekend trips usually 4 times a summer (Lake Ontario). Destinations are always plugin at dock. Does this help at all?
Found out that the alternator is a Motorola 51A
Cheers
2 Old Pirates
PS. Here is a new diagram, input is appreciated.
View attachment 162525
How were you thinking of wiring the alternator? Also, your starter battery is really just a spare/backup, unless you were going to wire it directly to the starter. Nothing wrong with what you propose, just clarifying.
 

Ward H

.
Nov 7, 2011
3,025
Catalina 30 Mk II Barnegat, NJ
We basically day sail. We have weekend trips usually 4 times a summer (Lake Ontario). Destinations are always plugin at dock.
This goes back to what @Stu Jackson said earlier.
If you are regularly connected to shorepower, DO NOTHING.
I upgraded my alternator because the original looked like it was dumped in salt water regularly and I was trying to avoid plugging into shore power when I was not at the boat. Started with 90A IR, then this season switched it to ER with the MC614 regulator. This so I could use Belt Manager feature as the 90A caused the belt to slip.

Then as I learned more about battery charging and how long it would take the 90A alt to bring my batteries to 100% SOC, I learned that what I really needed to do was plug into shore power at the dock.
I probably could have replaced the rusted alt with the same model or one of Compass Marines new 70A alt and been fine with just shore power charging.

In your diagram, you need a fuse between the charger and starter battery and between the house bank and battery switch. All fuses must be within 7" of the battery.

You might want to consider connecting your charger to just you house bank. Then wire a Blue Sea ACR between the house bank and starter bank. This allows for more efficient charging as the house bank is usually drawn down lower than the reserve/starter battery.

You also might consider a positive bus bar and bring both the charger and alternator wiring as well as the ACR to the positive bus bar. This will reduce the number of connections on the battery post.
 
Nov 16, 2012
997
Catalina 310, 2000, #31 31 Santa Cruz
So much info. We basically day sail. We have weekend trips usually 4 times a summer (Lake Ontario). Destinations are always plugin at dock. Does this help at all?
Found out that the alternator is a Motorola 51A
Cheers
2 Old Pirates
PS. Here is a new diagram, input is appreciated.
View attachment 162525
Maine Sail’s article, https://marinehowto.com/automotive-alternators-vs-deep-cycle-batteries/ has advice on options for a variety of boat uses. I’m sure you’ll find something in there that will work for you.
 
May 2, 2012
233
Catalina 310 Toronto
Checked out what both Marchem and Ward have said and came up with this. Which one?
Balmar Models.jpg


Cheers
2 Old Pirates

PS. I noticed on JK's diagram he used a Blue Sea 7610 in his setup which look very similar to what I want to do.
 

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