Weird wiring setup Larson Cabrio sports cruiser

[Zaria]

Hi folks,

We have just bought what yachties commonly call a "stink" boat

We bought a 2006 Larson Cabrio 260. The previous owners just replaced the batteries before selling so i just assumed the setup was good. Alas no!

It has 2 batteries and a "Guest" battery isolator switch. My experience in the past with boats is normally one of batteries is the start and the other is the house. Combining them normally in an emergency when the start battery is flat. Not in this case. Engine will start whether the switch is on battery 1 or 2!. All electronics work whether the switch is on battery 1 or 2!

Whats even more weird, is that the boat has a switching panel (Attached pic) which i have been told by the old owner that its for when shore power is hooked up only. Well, it has a Fridge switch on this panel, and even with all switches on this panel off, and no shore power connected, the fridge still runs. Basically the only way to turn the fridge off is to turn the battery switch to off, which means everything is off. There is no way to have the fridge off when using the boat !!

So my question is, i think i know how to fix the battery isolator switch by looking at the back, it looks like its wired up wrong. But i would just like to check with any other Larson Cabrio owners and how theirs are setup? Does anyone know if there is a Larson specific chat forum anywhere

cheers

[Sailmonkey]

What you describe is what I would expect from a 1-2-all switch.
In other words it’s wired properly for what it is.

Regarding the refrigerator, you’ll need to trace out the power supply for it to know why it’s on all the time.

[GordMay]

Your fridge may be a Universal AC/DC model (common in RVs & Power Boats), which will work with all power sources, including 12 and 24V DC, as well as 115 and 230V AC, both 50 and 60 Hertz.
Ie: ➥ https://www.westmarine.com/buy/isoth...03?recordNum=3

[tkeithlu]

The isolator switch does not control the starter circuit or the panel circuit. It simply lets you choose to draw from 1,2, or both. It still will do the starter backup task if you keep the switch on one of the two, and go to "all" or the other battery when you find it flat.

Have you traced the charging circuit? It probably charges only the active battery. In that case, assuming the two batteries are of the same type, you may want to run on both batteries while charging and then to hold a reserve switch to just one when not charging. Charging both while running on one would require diodes.

[peplefixr]

On my 310 the fridge in the cockpit is directly wired to the batteries so they can run at all times when switched on...Have seperate rocker switch to shut off if not needed.

[Flatswing]

Your set up is common on power boats that don’t do much anchoring overnight -usually dock to dock. The panel is almost certainly for ac only and your fridge is a dc/ac model(wag) - hardwired to battery output without a separate 12v switch, alternatively, you haven’t found the 12v switch yet.
A common way to run with this set up is to leave battery switch on “both” all the time except when anchoring overnight. When anchoring, switch to 1 or 2 leaving a good battery in reserve for am starting. Best not to switch while engines running unless you are certain it is a “ make, then break” switch or you might risk your alternator diodes.

[Shrew]

Originally Posted by Flatswing

Your set up is common on power boats that don’t do much anchoring overnight -usually dock to dock. The panel is almost certainly for ac only and your fridge is a dc/ac model(wag) - hardwired to battery output without a separate 12v switch, alternatively, you haven’t found the 12v switch yet.
A common way to run with this set up is to leave battery switch on “both” all the time except when anchoring overnight. When anchoring, switch to 1 or 2 leaving a good battery in reserve for am starting. Best not to switch while engines running unless you are certain it is a “ make, then break” switch or you might risk your alternator diodes.

Some of this is true. Much of it is balderdash.

Yes, it is common configuration with single engine powerboats.

It has nothing to do with dock queens. Both my previous and current boat are set-up this way:

1= Starting Battery bank
2= House Battery bank

All systems run on either bank, including Engine start (exactly like Gordmay's diagram). I sit on the house bank whether I'm at anchor, mooring, or dock. I start and run on the starting bank.

Both banks are completely isolated from one another with the exception of the isolation switch being set to BOTH. Setting the switch to BOTH with this configuration would make absolutely no sense. The objective is to isolate and preserve the starting battery.

In both boats, the house bank is significantly larger than the starting bank. It requires that as soon as you shut down the boat, the switch is set to the House Bank. Just before you start the boat, set the switch to the starting bank.

I'm installing a ACR and remote battery switches this spring. This will allow me to charge both banks while running and never have to manually flip the battery switch again.

[Redline452]

My previous sailboat had a similar arrangement for the AC/DC fridge; with AC off it would switch to DC and you had to open the lid and turn the thermostat off to stop it.

Not great when the shore power pedestal breaker tripped the evening before we left on a trip and it ran the battery flat.
I added a dedicated breaker so I wouldn't have to open it.

[Flatswing]

“Both banks are completely isolated from one another with the exception of the isolation switch being set to BOTH. Setting the switch to BOTH with this configuration would make absolutely no sense. The objective is to isolate and preserve the starting battery.

In both boats, the house bank is significantly larger than the starting bank. It requires that as soon as you shut down the boat, the switch is set to the House Bank. Just before you start the boat, set the switch to the starting bank.”

The above is what’s commonly espoused for cruisers BUT: many older power boats (even twin engines) have only 2 identical batteries. In many boats (no ACR) as explained by tkeithlu, you may need to combine using the Guest switch to charge both while you are running. Mine did, hence the comments about not switching with engine running.

[Zaria]

Hi folks,

Thanks for all the responses. For those of you who are saying that the setup looks correct, please open the attachment and tell me again that it looks correct.

As it makes no sense to me at all!.....cheers

[Flatswing]

Suggest you follow each cable carefully and hand draw a wiring diagram as you go. Double check anything that doesn’t make sense since it’s easy to mix up wires in a zip tied bundle or conduit. Then I think it will make sense to you. (I assume the “240v label refers to 12v output from your shore powered charger but you need to be very clear on this) Best to unplug everything & disconnect both batteries while u r rooting around in electrical panels until you completely understand what is 12v DC and what is 125/250v AC.
Remember in older boats, a black cable can be either 125v AC load or 12v DC neg. Some Asian built boats just have black welding cable for 12v +ve & -ve. P.O.s have been known to use whatever color wire they had rather than buy a new reel when making changes.
Typically on a boat, red cables should only be 12v DC but don’t assume this until you prove it to yourself.

Let us know what you deduce.