What battery?

[LoudDog]

The two battery post got me thinking...

So I have 5.7 L Mercruiser, have had it a few years. The battery that was it in when i bought it, and still in it is a marine deep cycle, group 24 (i think). I'm pretty sure it's starting to not hold a charge very long and I'm going to replace it. What should I get?

I always felt this battery was too small, I didn't quite know why it was a deep cycle and not a starting battery (as that is it's main job), and the motor doesn't always start as well as I'd like (maybe not enough juice?)...

thoughts? What do you use?

Thanks

 

[BigJ08]

Re: What battery?

Get another group 24, should be good to go. Many marine starting batteries are deep cycle.

 

[Utahboatnut]

Re: What battery?

If you only have the one I would go a cranking battery not a deep cycle. They are designed to deliver the juice in different ways. The cranker will give you the biggest bang all at once(needed to turn over a 350 V8) the deep cycle will give more of a constant but over a much longer period of time(as needed for electric trolling/long anchors with radio on etc. The deep cycle will start the engine but not really what they are best at. I also have seen combo batteries cranker/deep cycle. but have never used one myself. If you get one at an auto parts store just look at the reccomended one for that same year truck with a 350 and you should be fine. If you have a 24 now and end up with a 27 don't forget to buy a bigger battery box for the new battery.

 

[Bob_VT]

Re: What battery?

I use an interstate combo deep cell / starting battery w/o problems.

 

[Big Keepers]

A lot of unanswered questions

A lot of unanswered questions

Question: Do you have two batteries now or just one? Also do you have a battery switch?

If you have only one battery then you'll need to keep using a deep cycle battery or else your electronics will drain the starting battery too fast. First and foremost I'd check the condition of your positive and especially negative battery cables. A lot of the time your negative cable can become corroded inside the insulation which causes a lot of resistance. Too much resistance will prevent your alternator from charging the battery fully while the engine is running. The same goes for the positive. If they aren't thick enough that can also burn up the wire inside causing resistance. You also may want to test the alternator's output to make sure it is charging the battery effectively.

You may want to upgrade to a Group 27 Deep Cycle which will give you more cranking amps plus more amp hours. The amp hours are important because that determines how long you can run multiple accessories and electronics without draining the battery too low.

Depending on where you use the boat (lake vs. open sea) you may want to use a two battery set up if you don't already.

 

[windsors03cobra]

Re: What battery?

Duralast 1000 cold cranking amp/ 200 amp hour, 69 pound, group 31 monster from the Autozone. $100

 

[LoudDog]

Re: What battery?

I keep a spare battery on board just in case, but plan to go to a 2 batt set up.

I think I'm going to get a group 27 combo and then just a group 24 deep cycle.

Thanks all for the input!

 

[Big Keepers]

Re: What battery?

Do a search for battery switch or Automatic Charging Relay. I've posted numerous things about blue sea's add a battery kit. You basically take a deep cycle battery and hook it up to your electronics via the fuse panel or positive bus. The other battery is your starting battery which cranks the engine. The ACR is the relay that charges both batteries while the motor is running. Look it up, its easy to install and worth the investment ten fold.