3 batteries?

[gtmci84s]

I just picked up a '77 Silverton 28' fly bridge twin 318s and haven't gotten the chance to do anything with it yet. I noticed when I was looking at the boat before I bought it, that it has 3 batteries. 2 of the batteries sit directly next to each other and are attached to a 1-2-both switch (not sure what its called), and the 3rd battery sits off to the side and is attached to the port motor. Any one know any thing about this set up? I'm new to boats with twin motors so maybe this is normal and I'm asking a really stupid question? Thanks.

 

[Maclin]

Re: 3 batteries?

My first guess is the one connected to the port engine is a "Coach" battery (RV term, but have seen it used in the Marine theater) and runs 12v accessories on a separate circuit from the other two main batteries. It is attached separately like that to get charged when the port engine is running, assuming both engines have alternators. It is probably a deep cycle battery and is there to power things like automatic bilge pumps or other 12v accessories and 12v "coach" lighting in between cruises or while anchored with no shore power available. Totally guessing here with this advice, but the cost to you is reasonable

 

[gtmci84s]

Re: 3 batteries?

Thanks. They are all deep cycle identical batteries.

 

[MarkSee]

Re: 3 batteries?

Seems though on the port motor with only 1 battery, what happens if that battery dies and do you have a battery pack to jump start that engine?

Is there a shore power system installed on the boat and an a/c battery converter/charger installed to charge the batteries?

Typically, "deep cycle" batteries are better for running systems and can take deep discharges and not ideal for "engine starting" purposes as they don't have the cranking amps.

Nowadays, you can get "combo" batteries that have the best of both worlds.

Just some thoughts.

Mark

 

[gtmci84s]

Re: 3 batteries?

It does have a charger hooked to all 3 batteries. I'm wondering if maybe when the single one dies that's on the port engine, I can start my starboard engine and it will charge the port engine battery?

 

[MarkSee]

Re: 3 batteries?

Seems like you might need to trace any wires going to all the batteries and make a picture to fully understand what's going on and where, if any, improvements could be made.

I would think the starboard alternator is wired to the battery selector switch so both those batteries get charged at the same time but to think that same alternator could also be charging the port battery, you'd be seeing some other wire from the selector switch or some other type of connection device. Just doesn't make sense to me you'd want 2 alternators hooked up to the same battery directly.

Mark

 

[gtmci84s]

Re: 3 batteries?

That's what I might have to do is draw up a wiring diagram of it. When I went to look at the boat before I bought it, it was in dry dock and still had all of the batteries in it. I turned on the switch and was able to turn over the starboard motor, but there wasn't even any juice to the ignition for the port motor. So I assume the lone battery was just dead. I guess Ill find out this weekend when I go get it ready to splash.

 

[Silvertip]

Re: 3 batteries?

Deep cycle batteries can and often are used as starting batteries. Folks here have them on much bigger engines than yours.

 

[RogersJetboat454]

Re: 3 batteries?

The port battery is probably just for running the port engine (isolated from the house battery). Unless you have a problem with the port engines alternator, it's not just going to randomly die.

You could run a wire with a simple high amp switch between the batteries (connecting the starboard with port), keeping it normally open or off, then if you do happen to have one of the batteries go down, you will be able to start one engine, flip the switch and start the other. Chances are once you get all the batteries working, what's in there now for a set-up should be fine.

 

[gtmci84s]

Re: 3 batteries?

The port battery is probably just for running the port engine (isolated from the house battery). Unless you have a problem with the port engines alternator, it's not just going to randomly die.

You could run a wire with a simple high amp switch between the batteries (connecting the starboard with port), keeping it normally open or off, then if you do happen to have one of the batteries go down, you will be able to start one engine, flip the switch and start the other. Chances are once you get all the batteries working, what's in there now for a set-up should be fine.

I got the boat to my slip this past weekend and got a closer look at it. Looks like you're right, the port battery only runs the port engine and nothing else. The two (depending on switch position) on the starboard engine run all accessories and the starboard motor. Seems like a good set up really.