Outboard and ACR

[SitkaChum]

Hi,

A quick question about wiring in an ACR with an outboard motor.

I've got a Catalina 30 that I put a 25hp Suzuki outboard motor on the back of last summer, replacing a dead universal M4-30 diesel inboard. For far to many reasons to go into, it'll be a few years until I can repower with another inboard. In the meantime, the outboard pushes the boat far better than I could have hoped for. Currently, the outboard is wired to Group 27 battery that I installed in the rear lazarette where the propane tank used to store, connected with a simple on/off switch. The house loads are powered off a group 4D battery under the port settee in the main cabin, connected through a 1-2-B switch, with another group 27 that used to be the start battery for the diesel. The outboard circuit and the house bank circuits are not connected in any way. The house bank is connected to a charger hooked up to shore power. The outboard battery is not connected to any charging source except the outboard. The outboard is rated for 15amp alternator output, not huge, but better than nothing. Alternator output runs over the same wire as starting current - ie there are only two wires total to the outboard.

I'd like to connect the two banks so that the housebank will get some recharge when the outboard is running and so that the outboard battery gets a charge while on shore power. I don't want to do a complicated rewire of the entire boat as the ultimate goal is to get the outboard off the back and new diesel inboard, but it would be nice to put some juice back into the housebank on multi day trips. Currently, I charge up well before leaving the dock and manage loads very frugally. I was able to do 4-5 days last fall doing this, but came back with only a few electrons left. I'm thinking I could install an ACR between the outboard battery and the housebank with appropriate size wire/fuses. Does this sound feasible? Any other solutions that'd be simpler? To size the wire, I'd need to account for the maximum output of the outboard (15amp) and the length of the wire run, correct? Or do I need to size the wire for a higher load? Total distance between batteries is, I'm guessing 10-15 feet - need to measure the exact run when I'm at the boat in a few weeks.

Any thoughts and advice highly appreciated.

 

[Chief RA]

Put start battery down with house battery----hook'um up pos to pos-----neg to neg and run 15amp+ wire up to motor. Done! Chief

 

[Charlie Jones s/v Tehani]

Also remember that that 15 amp output is most likely at full throttle. You won't get anywhere that much running at lower throttle settings, which are usual when pushing a sailboat

 

[tommays]

My thoughts would be solar as even if it charged really well it would take motorboat hours to do much of anything

 

[Chief RA]

Tommays has the right idea but if you go that way just remember to add up ALL of your ampere use and pad it a bit. Solar panels tend to average about 50% of their amp rating over only about a 10 hour day.
Chief

 

[SitkaChum]

Thanks

Thanks for the quick replies. Appreciate the thoughts on combining the batteries, moving the start battery, and adding in solar. Solar might make some sense long term, however that'd involving adding in some brackets and such to support as well as trying to figure out how much usable sunlight is available. While the days are long during the summer in South East Alaska, they are often overcast or drizzly, which I'm assuming takes a big bite out of the efficiency of solar. As for just combining the batteries, for peace of mind I'd like to keep the start and the house banks separate. I can get by if needed without the house circuits - I have a handheld radio and GPS as backups and everything else except for nav lights is really just creature comfort at the end of the day - but not being able to start the engine if I do something stupid and leave something on makes me nervous.

I do appreciate the thought on the 15amps being MAX output and that real output under operating conditions is much less. I need to think about that some more.

 

[Stu Jackson]

KISS.

Really.

You have to make the conscious decision as to what a 1-2-B switch does.

Two things: USE switch or CHARGE switch or both.

One of the oft forgotten issues is that B on the 1-2-B switch does exactly what you're asking about, and the ONLY thing an ACR or combiner or Duo Charge or Echo Charge does is allow you to charge a backup/reserve/start bank without having to learn how to use the darned switch! Really.

Here are two posts that discuss it in detail. If you can't afford the ACR, the use a 1-2-B switch on B. I call B Backup, Backup, Backup if the ACR or combiner or Duo Charge or Echo Charge ever fail.

You CAN run a boat, simply and inexpensively, by simply learning two things:

1. It all depends on how it's wired

2. Figure out how the switch works, use it and don't let your brother-in-law touch it. EVER.

Good luck, should be rather simple for you.

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

 

[Benny17441]

By moving the battery away from the engine or connecting the house bank to the alternator output in effect you are increasing significantly the circuit's round trip distance. Consult a wire sizing chart as thicker wiring may be required.

 

[Joe A]

Don't forget the starter current

Put start battery down with house battery----hook'um up pos to pos-----neg to neg and run 15amp+ wire up to motor. Done! Chief

15 Amps alternator output sure, but don't overlook that the starter uses the same wires.

 

[Chief RA]

Good point Joe. Chief

 

[SitkaChum]

Thanks

Thanks for the thoughts everyone - Stu, I appreciate the articles you linked to - have read through them before and get the concept of the different ways to use the 1-2-B switch. Originally I had discounted the existing switch for two reasons - one, I had already, in my head, decided the best way to use the 1-2-B was to have alternator output going to house battery, etc and with the outboard using the same wire for start and charge I didn't have that option. Second, with the distance between the outboard and the existing wiring, it seemed easier to run a couple wires to put in an ACR instead of pulling a bunch of wire to wire the outboard into the existing system. After staring at the problem and kicking the it around it seems better to do it right then to just hodge podge something together for now. I'll be taking the outboard start/charge to the 1-2-B and put an ACR between the now primary and reserve banks. And thanks also to those that pointed out the need to size the outboard cable for the START current, not the charge current.

All the input is much appreciated - if anyone is ever at the docks in Sitka, stop by the Whisper and I'll have a cold beer waiting for you.