Upgrade Alternator to Balmar 120 amp OK?

6 posts / 0 new
Last post
sidthekid's picture
sidthekid
Offline
Joined: 6/1/16
Posts: 38
Upgrade Alternator to Balmar 120 amp OK?

All,

Have installed 2 Lifeline GPL-4DA AGM Battery Rated 210 amp hours for my house bank.

Our yard is recommending the Balmar 120 amp alternator, partly because the 100 amp is not available.

The yard has assured me it is fully compatible with my Westerbeke 35B engine.

On the Balmar web site, their product selection tool recommends the 70 or 100 amp models.

I note the 120 amp version requires a Dual Deep Vee Pulley which I do not have now.

Is the 120 amp model over powered for my engine?

Will the new pulley and belt setup lead to issues??

Thanks,

Bill L.

 

Bill & Barb
s/v Northern Lights
2002 Catalina 36 MKII #2086
Rock Hall, MD
Northern Chesapeake

True Wind
Offline
Joined: 7/15/12
Posts: 127

Sounds like a great idea. Just a FYI the alternator bracket is a cast aluminum and it is prone to breaking. Don't ask me how I know this.  

2003 Catalina 36

dlincoln3's picture
dlincoln3
Offline
Joined: 4/24/16
Posts: 132

I'm no expert at this stuff, but I'm going through a similar upgrade myself.  Maybe Mainesail will see this and chime in.  I have read that you're supposed to size the alternator output to be about 45% of the rated capacity of your battery bank for AGM batteries.  So if your total bank is 210Ah, then it seems that the 100A might be a better choice.  Or maybe you also have a starting battery to figure into the equation, which might lead to a different conclusion.  As to your pulley question, just make sure you have clearance inside the engine box for the additional stacked pulleys.  I change my pulleys to serpentines, and am pretty happy with the arrangement.  I had a clearance issue with the much wider serpentine belt and my Sherwood water pump, but your 35B won't have this issue since the pump is in a different location.

Don Lincoln
"Nancy Lynn"
1993 Catalina MK1.5, Hull 1238
LaSalle, MI (Lake Erie)
Universal M-35AC

Chachere's picture
Chachere
Offline
Joined: 10/27/10
Posts: 822

Sadly, Mainesail had a serious stroke last autumn and had to close down his shop, otherwise I'd recommend getting one of his alternators.   I bought a 105amp alternator from him in 2020 for our former C36 which had an M25 engine, and per his advice derated it to about 80 amps via the Balmar ARS-5H regulator.  Ran fine with a v-belt, and a smaller engine than yours (and running it derated allowed it to operate cooler).
 

Matthew Chachère
s/v ¡Que Chévere!
(Formerly 1985 C36 MKI #466 tall rig fin keel M25)
2006 Catalina Morgan 440 #30.
Homeported in eastern Long Island, NY

sidthekid's picture
sidthekid
Offline
Joined: 6/1/16
Posts: 38

Thanks for the replies!

True Wind - Is there a corrective action I could take in advance to avoid a broken bracket??

Don, yes, it appears 45% is a guide for AGM batteries. I am somewhat consoled by this quote on the Balmar web site regarding alternator selection - 

If you have a really large bank or a battery technology that calls for an alternator output that exceeds available alternator technology, then it will just take longer to charge your bank. Simply choose the highest alternator power which meets your budget and pulley constraints.

So leaning towards the 100 amp version but staying with the single v pulley.
 

Bill & Barb
s/v Northern Lights
2002 Catalina 36 MKII #2086
Rock Hall, MD
Northern Chesapeake

True Wind
Offline
Joined: 7/15/12
Posts: 127

I have had two of those flimsy cast aluminum alternator brackets break. I bit the bullet and took the broken bracket to a machine shop and had them make me one out of real aluminum. Been on for years with no problems.

I have the same M35B engine. I installed a Balmar 120 amp alternator with an external regulator. I also installed a J10 belt system. Plus, I throttled down the alternator output with the external regulator to around 90 amps. I'd be a little bit concerned with using a v-belt on a 100 amp alternator.

2003 Catalina 36

Log in or register to post comments