posted 02-10-2001 02:21 PM ET (US)            

I have not actually tried either of these arrangements myself. I plan to re-wire my dual-battery/dual-engine boat this spring, as the current wiring seems to cause the charging coil on one engine or the other to burn out, probably due to some strange currents occuring from the prolonged connection of the two charging circuits to a single battery bank.

Although not as flexible, I may go with the easier to operate 3-switch arrangement. As long as the tie switch is not closed, the two engines and batteries are entirely separated and cannot be accidently connected by inappropriate setting of the other switches.

It is also a little simpler to wire.

posted 02-10-2001 04:50 PM ET (US)            

I don't see how there's much difference in
how hard to wire they are.

Each has advantages. Original allows either
battery to start either engine. Get one
running, let run for a few minutes to charge
the battery back up, start the second.
Alternate does not allow this.

Alternate allows both batteries to start
either engine. But doesn't allow just the
other battery to start it. Primary doesn't
allow this.

I can see where you would want both of these.
I'd use the primary, and add a paralleling
switch. That would give you the best of
both worlds:
Impossible to have an engine that doesn't
have a battery.
Can start from the other battery.
Can start from both batteries.

I don't see where single battery, dual
engine is going to blow things. I'd look
elsewhere for the source of that problem.
A short?

posted 02-10-2001 06:03 PM ET (US)            

1) The "Whaler-Factory" wiring does allow the paralleling of the batteries.

That happens when either of the OFF-1-2-ALL switches are in the ALL position. They suggest having them both in the ALL position.

---

2) As for my situation, I have scratched my head about it for some time, drawn diagrams, etc., trying to figure out what has happened, but the sad truth is that shortly after spending $300 getting the charging coil replaced on the PORT engine, the coil opened on the STBD engine. It might have been coincidence, but I think something is going in with two alternators charging one battery.

This is my best analysis: if the PORT engine charging system raises the battery voltage to a certain level, say 15.0 volts, and the STBD engine charging system is only producing 14.4 volts, then from the point of view of the STBD engine's charging system it is looking at an open circuit.

Current from the PORT engine's charging circuit would try to flow into the STBD engine charging circuit. Now, there are diodes which prevent this, but the effect of reverse biasing the diodes is to remove the load of the battery from the charging circuit. Then you are back to the forbidden case: operating the engine with no battery to absorb the charging current.

I think that is what is happening to my (over priced) charging stators.

Therefore--any theoretical objections aside--I plan to completely overhaul the wiring in the back of the boat to eliminate the present situation where both engines are paralleled to one (bank of) battery(s).

posted 02-10-2001 06:12 PM ET (US)            

I say that the "alternative" wiring is a bit simpler due to the fact that if one were to locate the OFF-1-2-ALL switches at opposite sides of the boat, then you have to run more wiring across to connect them.

I made the assumption that the batteries would be located one on each side of the boat. That is how they are in my 20-Revenge. There is a battery case in each extreme outboard end of the engine well, thus the batteries are located far apart. The OFF-1-2-ALL switches would likely be located on the cockpit bulkhead in front of the engine well. Thus you would need to run three pieces of 2-AWG cable across the boat to tie them together.

In the alternative arrangement, you only run two pieces of 2-AWG cable across the boat.

Now if you locate the batteries and the switches all close by, then there is not much difference.

posted 02-11-2001 09:58 AM ET (US)            

In a sense I am glad to hear that this has happened to someone else; I was beginning to think there was something weird going on in the boat wiring on my 20-Revenge. Sorry about those blown stator coils.

I would also like to ask if anyone can describe the wiring between the battery negative, the fuel tank, and the zinc anode.

My boat is in storage and not convenient to visit, so I can't refer to it for guidance.

Also, is there something installed in the ground/negative line on your boats? There is a small black plastic gizmo wired in the negative lead on my boat (I recall), and I am thinking it might be some type of noise filter for the electronics, or else it is a galvanic isolator. Anyone have a similar gizmo in their ground (green) wiring?

posted 02-11-2001 10:26 AM ET (US)         

Ground Wires: The first wire runs from the ground lug on the fuel tank directly to the anode on the transom. The second wire runs from the ground lug on the fuel tank to the negative side of the batteries. The third wire runs from the fuel tank ground lug to the fuel tank filler assembly. There should not be any splices in the fuel tank ground wires.

posted 02-14-2001 11:48 PM ET (US)            

Running two engines from one battery is exactly what you must avoid, otherwise you may damage the charging system of one of the engines.

The two chargers seem to buck each other until the strong one burns out the weaker one. Then things go just fine, but you have one engine with a burned out charger.

You don't necessarily even notice this because the good engine keeps the battery charged.

posted 02-15-2001 12:33 AM ET (US)            

I also discovered while browsing the West Marine catalogue that they are fans of the alternative arrangement.

posted 02-15-2001 09:45 AM ET (US)            

Provided the tie switch isn't thrown. If
you throw the tie switch you can flatten
both batteries.

I think I'd clearly label the normal position
of all switches.

posted 05-28-2001 07:59 PM ET (US)            

I have added a schematic diagram to the REFERENCE article (see link above in first message) and some comments about the design.

One thing I like very much about the "new" arrangement is its extreme simplicity. It is being used, after all, on a small boat.

There is not that much room in the rear cockpit or motor well for multiple switches and multiple batteries. This wiring was very simple and yet it provides all the flexibility I think I will need.

Of course, after a season of use I may have a different idea. For the moment, we have the boat wired as shown and we'll see how it works!

Comments are invited, as always. A group discussion often produces new ideas and improves thinking.

posted 08-07-2002 05:01 PM ET (US)            

In the 'new' schematic, since the batteries are each ALWAYS connected to the engine charging systems, you would never have to worry about burning out a coil because it's impossible to run either engine without being on line to a battery. Is that right?

In the normal operation section when both engines are running, the center switch can be OFF, 1 or 2? Anyplace but on Both, right? (on off you would have no house power, though?)