Old alternator, new choices

[Ekutney]

I currently have an "original" Motorola 8RG2009A alternator & it took me 2 weeks of PB application & patience to get the pivot bolt free.  It was bonded from the bolt to the alt frame.  PB did the job.

I am looking to have the alt tested & then determine my next step & trying to keep a tight budget.

I have 2 GC T105 & a group 24 for reserve/starting. My use is weekend on the hook & back to marina. Motoring at times for a couple hrs at the most.  I have a Sterling 30 amp charger, excellent purchase from Mainsail. It will keep the batteries maintained & I currently have no solar.

Based on my use & current config can i just put the alt back on if it tests OK or is an external reg the best way to go?  I've searched this topic on older posts & I got the gist this alt does not do a very good job, am I correct?

Any suggestion as to smart choices would be appreciated.

[Stu Jackson]

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I have 2 GC T105 & a group 24 for reserve/starting. My use is weekend on the hook & back to marina. Motoring at times for a couple hrs at the most.  I have a Sterling 30 amp charger, excellent purchase from Mainsail. It will keep the batteries maintained & I currently have no solar.

Based on my use & current config can i just put the alt back on if it tests OK or is an external reg the best way to go?  I've searched this topic on older posts & I got the gist this alt does not do a very good job, am I correct?

Any suggestion as to smart choices would be appreciated.

The smart choice would be to continue to use what you have BASED ON HOW YOU USE YOUR BOAT.

The major reason to upgrade the alternator and add eternal regulation is primarily for those choose to use their boats differently than you.  Those folks, like me, enjoy anchoring out or cruising for extended trips, more than one night.  They not only desire but actually NEED to produce as much input amperage as possible in as short a time as possible without plugging into shore power.

Whether solar and/or a generator are involved is also not the issue, because they are merely additional charging sources when cruising, and do not impact the question you are asking. 

For a single night or two out and returning to a marina to plug in each or every other day, the OEM alternator with internal regulation (at the proper voltage setting) will be just fine.

Cruisers think: I start the day with my batteries drained, how can I get the most back into them.

Short term cruisers or marina hoppers think:  my batteries always are full when I start out, how long can I go [based on my energy use and house bank size] before I have to plug in again.

That's how it works.

[mark_53]

Ed:
I have to agree with Stu, it all depends on how you use the boat.  There are many options to recharge batteries, however aside from plugging in to shore power, the upgraded alternator will provide the fastest most reliable means to charge batteries.  I use my boat similar to you and have the OEM 51amp alternator.  I've done 3 or 4 day's on the hook but I don't use refrigeration, fans or heating other than a oil lamp and have LED lights.  Recently I've started bringing along Yamaha 2000 W portable generator because I like hot water showers and to recharge house batteries if needed.  If I add a new power source, it's likely to be solar because it's fairly inexpensive, and not as dirty as an upgraded alternator.

[mainesail]

I currently have an "original" Motorola 8RG2009A alternator & it took me 2 weeks of PB application & patience to get the pivot bolt free.  It was bonded from the bolt to the alt frame.  PB did the job.

I am looking to have the alt tested & then determine my next step & trying to keep a tight budget.

I have 2 GC T105 & a group 24 for reserve/starting. My use is weekend on the hook & back to marina. Motoring at times for a couple hrs at the most.  I have a Sterling 30 amp charger, excellent purchase from Mainsail. It will keep the batteries maintained & I currently have no solar.

Based on my use & current config can i just put the alt back on if it tests OK or is an external reg the best way to go?  I've searched this topic on older posts & I got the gist this alt does not do a very good job, am I correct?

Any suggestion as to smart choices would be appreciated.

The 8RG2009A is the regulator not the alternator. That regulator is factory set at 14.2V and won't do you too many favors with batteries that prefer to be charged at 14.6V to 14.8V, especially when sensing the alt end of the circuit. Your alternator is most likely a 51A and while pretty small, it can do a better job with a Leece-Neville adjustable regulator set to to 14.4V - 14.6V or, depending upon how much you motor, even 14.7V -14.8V. That alt can also be converted to external regulation but you're still starting with a 51A alt...

I have bolt on genuine Leece-Neville regulators to fit that alt, which can be set up to remote sense. You just need to make sure the alt has two AC taps one on the left and one on the right as this is a self exciting regulator. I have a lot of alternator options to fit Catalina's..

https://shop.marinehowto.com/t/alternators--regulators

In a few weeks we will begin shipping our new CMI-72-IR "Catalina Special" alternator. It is a 72A 8MR frame with billet machined 3/8" pulley, adjustable regulator, bi-directional fan, high output diodes and a 10mm to 3/8" fit sleeve. Pricing will be under $300.00. This is a fully custom alternator that does not exist within the Leece-Neville product line. We specifically intended it for drop-ins on boats with Universal engines who just want a basic improvement over the stock set up and who want a basic VR that is adjustable.. 

[Ekutney]

Thanks for the clarification on the part number, regulator not alternator. I assume alt # is 8MR2049K with additional stamp of 12N-51A-8440.

I plan to update what I have with the Leece-Neville regulator then update the alt for the following season when I add another 2 T-105s.  I am waiting because I also plan to add a SG-200 & have a budget to keep in mind.

Thanks for the comments, I thought explains my use of the boat would be helpful when deciding where to spend the boat bucks.