I have a Catalina 34. Wanting to upgrade my alternator. The Catalina site shows a prestolite 105 they say will work. Any input, ideas?

Jan 11, 2014
7,824
Sabre 362 113 Fair Haven, NY
There is more to upgrading an alternator than just installing a new larger one.

There will be little advantage to the larger alternator if it is an internally regulated alternator. The internal regulators are typically not set up for charging deeply discharged batteries and are not adjustable for different battery chemistries.

A 3/8 inch single belt is not sufficient to drive the alternator without a lot of belt wear. At 90-100 amp it is necessary to move to a double belt or serpentine belt. The larger alternator will also place more pressure on the adjusting bolt causing it to slip.

The articles on MarineHowto.com provide a good overview.

MarineHowTo.com - Alterntors & Regulators
 
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Feb 6, 1998
11,436
Canadian Sailcraft 36T Casco Bay, ME
Wondering if I need to change anything like a pulley?
If you want to use that Chinese clone alternator from CD you'll need to convert it to external regulation as the 3/8" belt is going to really suffer. This is why we build our CMI-72-IR model..
 
Mar 6, 2008
690
Catalina 1999 C36 MKII #1787 Coyote Point Marina, CA.
It also will require additional horse power that is provided by the engine. The original alternator generates about 14.2 vdc and I have monitored as much as 21 amps.
 

J Spry

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Jun 17, 2021
4
catalina 2006 Catalina 34 Safe Cove
If you want to use that Chinese clone alternator from CD you'll need to convert it to external regulation as the 3/8" belt is going to really suffer. This is why we build our CMI-72-IR model..
I just left my info with them. I will see what they suggest. Thanks
 

J Spry

.
Jun 17, 2021
4
catalina 2006 Catalina 34 Safe Cove
There is more to upgrading an alternator than just installing a new larger one.

There will be little advantage to the larger alternator if it is an internally regulated alternator. The internal regulators are typically not set up for charging deeply discharged batteries and are not adjustable for different battery chemistries.

A 3/8 inch single belt is not sufficient to drive the alternator without a lot of belt wear. At 90-100 amp it is necessary to move to a double belt or serpentine belt. The larger alternator will also place more pressure on the adjusting bolt causing it to slip.

The articles on MarineHowto.com provide a good overview.

MarineHowTo.com - Alterntors & Regulators
Thank you I will follow up.
 
Oct 26, 2008
5,011
Catalina 320 Barnegat, NJ
If you decide you want to add a serpentine pulley, you might want to check the clearance on your engine cover. If I remember correctly, the install is similar to my Cat 320. I added the serpentine pulley to my 125 amp alternator (previous owner upgrade) and found the pulley rubs the inside of the cover until I pulled the cover out an inch. I haven't worked out my solution yet (I'm just living with the inch gap this summer) and I suspect that the P.O. didn't buy the serpentine pulley for that reason.
 

J Spry

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Jun 17, 2021
4
catalina 2006 Catalina 34 Safe Cove
Thanks. I was wondering if that might be a problem. There isn’t a lot of room as it is.
 

MitchM

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Jan 20, 2005
960
Nauticat 321 pilothouse 32 Erie PA
i'm familiar with a few yanmar owners who decided to 'upgrade' their alts from the stock that yan put on as OEMs. they hd nothing but trouble. so check your engine mfgr's specs VERY carefully to avoid a lot of untold aggravation. mainesail is right . (as usual...)
 

NYSail

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Jan 6, 2006
2,736
Beneteau 423 Mt. Sinai, NY
Speak with Maine Sail. I followed his recommendations and my upgraded alt that I purchased from him works as advertised. Yanmar 4JH4E……

good luck
Greg