In installed an Ample Power charging system in 2000, also replacing the wet cell 4D batteries with 4D gel cells. The alternator is about 100 amps along with a battery monitor, voltage regulator and echo charger for a separate Optima starting battery. I anchor out whenever I use the boat; now that I'm retired I'm usually away from the dock for 3-4 days. I usually charge an hour in the morning to top off the batteries. If I don't do any motoring (which I avoid like the plague), I may need to run another hour every couple days. The battery monitor helps keep track of voltage and the charge state, along with amps being consumed/added and lots of other stuff. I find it invaluable for keeping track of energy use, charge rate and how much I'm consuming at any point in time.

My batteries were still going strong as of the end of the 2011 season, so I'm more than pleased with my system.

You can buy a 90 amp Leece-Neville (Prestolite) alternator that is a direct bolt in replacement for the stock 55 amp one. You will want an 8MR2070 or an 8MR2069, one is metric one is imperial, I think that is the only difference. I used the 2069. They are far cheaper than an aftermarket one ($200 in Canada, likely a lot less down there) and they are a heavy duty marine alternator. Parts for these are readily available at just about any automotive alternator rebuilder shop.

I used the Prestolite conversion unit to convert it to external regulation and got 2 brand new Xantrex XAR regulators (gotta have spares) for $150 on eBay. Pretty sure the Balmar ones are Xantrex XARs rebranded, they look the same as mine.

Maine Sail has two good articles on this pretty simple job:

Alternator conversion:
[URL]http://www.pbase.com/mainecruising/alternator_conversion[/URL]

90 amp alternator upgrade:
[URL]http://www.pbase.com/mainecruising/catalina_36_alternator[/URL]

It works very well for us. We usually run 1/2 hour morning and evening getting on and off anchor and that keeps us good to go. But that's along with a 220 watt solar panel and 200 watt wind gen.

No matter what you end up going with, don't mount the external regulator in the engine room, the heat will kill it. Ours is mounted on the wall behind the engine in the aft cabin where it does not get a lot of heat.

Sam,

Since you are planning on a lot of cruising, you might want to seriously look at adding at least 200W of solar panels and a controller. It isn't cheap to do so, but the advantages are great: silent, reliable charging if you spend most of your time in sunny climes, no engine noise and wasted fuel just for charging batteries, and less wear and tear on your main engine.

We have 480W of solar panels and have gone as much as 100 days with essentially never running the engine to charge batteries and never plugging into shore power.

Just something to think about. BTW, we also have a Balmar 100A alternator and smart external regulator for those rare times when we have little sun for 2-3 days.

Sam,
We changed out to the 90AH Leece Neville when we purchased our C36. I previously had a C34 and made the same mod on it and found it worked great. The 90AH can use a single belt and the case is identical to the OEM, so it is a very easy change. We use a Balmar external regulator (and like Bud, I have a spare onboard) which we mounted behind the tall skinney door next to the sink. I had to extend the harness a little but this way the regulator is away from the heat of the engine compartment. I also installed temperature sensors on both the alternator and battery bank. The alternator output is connected directly to the house bank with a 4 gauge cable (fused with a 100 amp fuse at the battery) and we rely on a charging relay to keep our backup starting battery charged. As far as I can tell we use around 100 AH/day when cruising (fridge is the big draw), so motoring/charging 1 to 1.5 hours per day seems to keep us fully charged when away from shore power. I think the external regulator is important to getting amps into the battery bank, but so is having an adequate sized cable coming off the output. I like having a separate cable direct to the house bank since it eliminates any chance of killing the diodes while switching. This is a really easy project but you need to use correct wire and connectors (proper crimps, adhesive heat shrink, etc.).
Along these lines the best change we made was the move to 4 6v batteries for the house bank, giving us better than 400AH. I was struggling to figure how to make them work with the existing boxes, which are designed for 4d's, until I read Jack Stewart's article about simply cutting and lengthening them to hold the 6v's. Fit is a little tight but it works.

Sam, in line with upgrading your alternator, you should follow the advice of moving your alternator output to the house bank.

Here are ways to do it: [url]http://c34.org/bbs/index.php/topic,6604.0.html[/url]

Don't know about your background in boat electrical systems, but here's a passel of links: [url]http://c34.org/bbs/index.php/topic,5977.0.html[/url]

[QUOTE=Capt. Sam;11859]I'm planning an extended cruise and plan on anchoring out most of the time. I've got these humongous heavy duty batteries that the PO installed and I'm concerned that the standard altenator that came on the Universal M35 will not keep them fully charged. My electrical consumption will consist of the fridge, auto pilot, lights, water pressure pump and stereo while cruising.
Has anyone upgraded to a heavier altenator? Any recommendations? How about instead of replacing the one I have, adding a heavier on an a separate bracket? Leaving the original wired to the isolated engine start battery and the new larger on to the house bank? I've searched the site and can't find any info on this.
Thanks
Sam[/QUOTE]

Sam, I have a C-375 with 2 4D house bank (340 AH) and lots of energy consumption when cruising with two refridgerators. My Yanmar Diesel has an 80 amp alternator but I hate to run my diesel just to charge batteries. My solution was the $1000 Honda 2000 generator and an upgrade to a 70 amp battery charger for the house batteries. The Honda is a quite and efficient way to recharge by batteries. With a 50% discharge on the batteries my Honda takes about 2 hours to recharge back to 90%.

Rod Tennyson
C-375 Lila Jean