Repowering Wiring Question

[Analgesic]

So, I decided to repower my 1988 Mark I this year, moving from a Universal M25XP to a Beta 25 which is presently resting in the engine bay not yet hooked up. I took the opportunity to make an accurate wiring diagram at last after 20+ years.  The most immediate discovery was that the Universal had 3 heavy gauge red wires going to the engine, one fused going from the 1-2-Both switch to the starter motor and the other two unfused going directly from I presume the alternator to the house and starter batteries respectively.  The Universal had a Balmar 100 amp alternator with external regulator which I removed (no clear way to hook it up to the new alternator which I was told is internally regulated).  The Beta has a 70 amp alternator (I recently added 220 W of solar) and only one + lug on the engine block for the starter. 
So, putting together what I've researched on this site, my plan was to remove the two excess heavy red cables so all positive power goes through the 1-2 Both switch bidirectionally, to start the engine and charge batteries.  I will add either a Blue Sea ACR or possibly a Victron Cyrix-ct (which appears to do the same thing at half the price) echo charger.  The connection will be fused close to both the house bank and the starter battery.  Does all this make sense or am I missing something?  Thanks for any guidance and/or experience you can share. 
Brian McPhillips 

[Jon W]

Will your alternator output connect directly to the fused positive on your house bank then go to the 1-2-Both switch?

[Analgesic]

The house positive goes to the 1-2-Both switch, then a short run to a big fuse, 300 amp I recall, then straight to the engine block positive post which attaches to both the alternator and the starter, Beta's design.  As I understand it, power will be flowing in both directions, towards the engine to start, then away once running to charge.

[waughoo]

I know you didnt ask for this answer, but here' goes...

You could keep the balmar alternator and regulator.  It is possible to get a new alternator pulley for the balmar so that it matches the multigroove of the Beta engine.  This would allow the current high voltage wiring to stay the same from your old engine to the new.  Plus the remote regulated alternator is more feature rich and flexible (battery chemistry) than the internally regulated alternator.  If it were me, I wouldnt want to give up my externally regulated alternator.

[Analgesic]

Thanks Alex.  For now I have pretty good golf cart batteries but am considering the switch to Lithium once they die.  I'm already in for many years of boat bucks this Winter so I'm looking for the simplest/cheapest answer right now.  I kept the Balmar alternator for possible future use after donating the rest of the Universal.  My old Balmar regulator died many years ago and have been using an automotive regulator since.  My simple goal right now is to launch the boat in May with a reliable engine and not start a fire when I turn the key!   

[Ron Hill]

Brian : I'm a believer that what you want to charge is the battery/ies: So why not take the alternator output and wire it direct to the battery/ies??  I did that 25 years ago and never have had a problem!!

A thought

[Ron Hill]

Brian : I'd surely figure out a way to get that Balmar 100 on to your new Beta. With the external Voltage regulator you are much better off (electrically)than with the internal regulator alternator.

Keep the one that came with the engine as a spare!!

A few thoughts

[waughoo]

Ron,

If you read a few posts up, Analgesic answered why he chose not to do that at this point and time and that he DID sa ve the 100a alt to perhaps fit it later.

[Stu Jackson]

Brian,

I hope you have read the Electrical System 101 topic, especially these:

OEM 1-2-B Switch Wiring History  http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

1-2-B Considerations (New 2020 - Rod finally got around to diagramming what I had done in the above link in 2009 :) )
https://marinehowto.com/1-2-both-battery-switch-considerations/

Basic Battery Wiring Diagrams  This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring:   The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615

This is a newer primer for boat system wiring design with a thorough diagram:   Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/index.php?threads/building-the-dc-electrical-foundation.181929/#post-1332240

The Short Version of the 1-2-B Switch Stuff:  http://c34.org/bbs/index.php/topic,5977.msg38552.html#msg38552  This is a link to the Electrical Systems 101 Topic, reply #2

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The Universals did not come the way you describe what you found.  The PO changed the wiring.