[aiwa711]

Ok so I have a 1989 3100, I replaced a 35watt professional Mariner with a 12-40 promariner 3 bank battery charger. I’d post pictures but I don’t know how.

My question io have 3 batteries and only two wires going to the charger? The two wires go from the charger to a 40amp fuse then to a “stator” maybe? A bunch of wires are connected to it very large wires going to each alternator then to the engine batteries. I have an isolater also. I am wondering how my house battery is getting charged if only I have two wires going to the charger. Does anyone else have this going on. Or is there another charger?

I also put new lights in the bathroom!!

[Uhehner]

I think you mean you have two cables going to the charger and you have a 12 volt 40 amp three bank charger. One cable should have 3 wires for 120 volt AC from your circuit breaker AC panel, a black (hot), white (neutral) and green (ground). The other cable should have 3 red #8 AWG wires going to each of your batteries, usually via the battery disconnect switches and one black (or yellow) #8 AWG wire going to the battery negative terminal usually via the engine block.
If you do not understand this or have any doubts I suggest you get a marine electrician. An incorrectly connected charger can cause severe engine, propeller, shaft and through hull electrolysis damage.
Capt. george

[aiwa711]

I understand completely. I am saying that I have two red wires going to 40 amp fuses then to a stator like device. I know I have a 3 bank battery charger. I’m charging all 3 batteries. I am wondering why all 3 batteries are not hook up to the charger yet all 3 get charged.

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I understand the 3 wires going to ac. The charger works great. I’m just wondering how my “house” battery gets charged

[jclark003]

Are you sure you have three separate battery banks? I've seen some installations that have a start bank that services both engines along with a house bank. One engine alternator charges the house and the other charges the start. That could explain why you have only two charge wires. Alternatively with your setup one wire could go to the house battery, the other going to an isolator that feeds two independent start batteries. This may have been done because the previous charger only supported two bank charging.

Regardless it would seem to make sense with a three bank charger to wire direct to batteries (assuming you do have three separate banks), leaving the isolator in place for the alternator to charge two independent batteries.

If unsure follow Uhehner's advice and get a marine electrician to give you a hand. There are a lot of different ways to wire in charging systems.

[aiwa711]

That’s the funny part, my charger is from the year my boat was made. 1989! And that’s how it was hooked up. AND it was a 3 bank battery charger. That’s why I am confused

[jclark003]

no ideas unless the original wiring of that model was configured for a 2 bank system and the three bank charger came later?? if that module is an isolator I would think you are fine to leave it wired as is. Your charger will put out as much current as it can regardless of how many output legs are being used. If you want to be sure have someone knowledgable look at it.

[Uhehner]

I always use a digital volt meter to test a battery charger. With the engine and charger OFF take a reading on each battery. It should jump up to 13.8 volts when the charger is turned ON. If there is an isolator in the circuit you will loose about a 0.7 volt drop through the diode but you will still see the battery voltage jump up to about 13.1 volts when the charger is ON. Use the same test to check your alternators when the engines are running and shore power is OFF.
If your boat wiring is original you could look at the Tiara DC schematic to see the hook up. Tiara can email you this information.
Capt. George

[aiwa711]

Update, so I checked the charge of the batteries. Port side battery was good starboard and house must be linked somehow, voltage was exactly the same compared to the port side battery. So everything was hooked up correctly and is charging/maintaining the batteries well! I’m happy about that. I checked them all with the charger on and off. And turned the charger on to see if it spikes up and it did so.