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TOPIC: I hate 8D batteries. Replace with a pair of 27s or 31s?

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 15:25 #1

  • Cptmorgan
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My port 8D start battery is dead. The starboard start 8D is just fine.

I figure I can replace the 8D with a pair of group 27s or 31s for the same price as an 8D, and have a net gain in AH and MCA. Anyone using pairs of 27s or 31s as start batteries?

The Cummins BTAs need at least 1200 MCA in my experience. The preheaters are a battery killer.

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1997 Bayliner 4788 "Mostly Harmless"
Sold: 1990 Bayliner 3888
Last Edit: by Cptmorgan.

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 16:10 #2

  • Norton Rider
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I believe that there are a few people in this forum running a single group 31 battery per engine. There are readily available group 31s rated at 1100 and 1150 CCA.

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1999 3788, Cummins 270 "Freedom"
2013 Boston Whaler 130 SS
Anacortes, WA

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 16:20 #3

  • iceclimber
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www.walmart.com/ip/EverStart-Maxx-Marine...p-Size-29DC/20531539

Been using these for years, yeah lower CCA, but also 100 bones, or even cheaper if you pass on the warranty. Paired up they do just fine, or even as a single.

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I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 16:42 #4

  • Uncle Bob
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I changed my factory set-up of a dedicated starting battery for each engine to start both from one 8D. One alternator does the start battery and the other the house. Handles the pre-heaters fine. In other words one battery works well. It won't care if you get the cranking amps from an 8D or another configuration. Edmonds battery is a good source.

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1989 26' then 1994 32' now 2001 39'

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 17:10 #5

  • aluxury1
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This one battery should last and do the job for quite a long time thus being the "best deal" for the dollar.

www.amazon.com/NorthStar-Ultra-Performan...attery/dp/B00P1K6EPE

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Brett
2001 Ciera 2858 EC
2007 Mercruiser D'Tronic 250
Sane people, tossing good money into a hole in the water!

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 18:51 #6

  • cosmo777
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On our 4788 (with 330 Cummins), I pulled out both 8Ds and installed Grp 31's - one for each engine.
Been this way for 2 years without a problem. Pre-heaters stil in place (not unplugged).

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Pat
Paragon
1999 4788

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 19:01 #7

  • Norton Rider
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cosmo777 wrote: On our 4788 (with 330 Cummins), I pulled out both 8Ds and installed Grp 31's - one for each engine.
Been this way for 2 years without a problem. Pre-heaters stil in place (not unplugged).


Do you boat year round? have you had any problems starting the engines in below freezing temperatures? I realize the water in our area stays between 45 and 50 degrees, but the lazarette will be somewhere in between the outside temperature and the water temperature.

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1999 3788, Cummins 270 "Freedom"
2013 Boston Whaler 130 SS
Anacortes, WA

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 20:09 #8

  • SomeSailor
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My truck with a Cummins 5.9L has two Group 31 batteries. Don't see why that wouldn't work well on a boat.They're Optima AGMs and are 900 CCA each.

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I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 21:14 #9

  • Cptmorgan
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Last winter, when the 8D started to show signs it was near the end of its,life I tried a single new Group 31 Deep Cycle flooded from another project to see how it would perform (1000 MCA / 833 CCA). The little 31 Deep Cycle was noticeably slower to crank in the cold weather than the near death 8D, so I ended up leaving it alone. Now that the 8D is truly dead, I need to fix the problem. I'd like 1200+ MCA to start the boat in the cold.

I'm running Blue Sea Battery Isolaroter/Combiners. I'll stick with a dedicated bank for each engine.

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1997 Bayliner 4788 "Mostly Harmless"
Sold: 1990 Bayliner 3888
Last Edit: by Cptmorgan.

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 21:43 #10

  • Old Man With A Boat
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I have one 8D to start both engines. It has been this way since I bought the boat in 2002. Replaced it in 2012. It works great.

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Just love being on my 3870............Bill
1985 3870
Twin 130 Mits. not turbo charged
Name of boat is "Plenty Of Fish"
Live on board full time.
North Myrtle Beach, SC

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 23:04 #11

  • bal734
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baylinerownersclub.org/index.php/forum/m...-8d-starting-battery

I have one group 31 per engine. Still going strong at six years.

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"Impasse". 2001 3988
Cummins 330's
Puget Sound

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I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 23:19 #12

  • Norton Rider
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Cptmorgan wrote: Last winter, when the 8D started to show signs it was near the end of its,life I tried a single new Group 31 Deep Cycle flooded from another project to see how it would perform (1000 MCA / 833 CCA). The little 31 Deep Cycle was noticeably slower to crank in the cold weather than the near death 8D, so I ended up leaving it alone. Now that the 8D is truly dead, I need to fix the problem. I'd like 1200+ MCA to start the boat in the cold.

I'm running Blue Sea Battery Isolaroter/Combiners. I'll stick with a dedicated bank for each engine.


To answer your original question, I don't think there's any doubt that two group 31s in parallel for each engine will work, since they will provide as much or more CCAs than an 8D.

In my mind the question is whether a single group 31 per engine will do it. In your experiment you used an 833 CCA battery. That's 28% less cranking power than a Northstar 1150 CCA group 31 battery. Here are the Cummins requirements for a 12 Volt starting system on a 6BTA marine engine. Note that JW stands for Jacket Water Cooled (like the 270 HP engine) and SW stands for Sea Water Cooled:

Minimum Recommended Battery Capacity
6B/6BT/6BTA-M (JW) Cold Soak at -18°C (0°F) or Above - Cold Cranking Amperes (CCA)... 950
6BTA-M (SW) Cold Soak at -18°C (0°F) or Above - Cold Cranking Amperes (CCA) ................ 1100
Reserve Capacity - minutes ........................................................................................................160

For comparison, here are the Northstar NSB-AGM 31 specs:
CCA rating at -18°C (0°F) 1150 A
CA/MCA rating at 0°C (32°F) 1370 A
Reserve capacity 220 min

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1999 3788, Cummins 270 "Freedom"
2013 Boston Whaler 130 SS
Anacortes, WA

I hate 8D batteries. Replace with a pair of 27s or 31s? 30 Aug 2017 23:56 #13

  • Johnny Vintage
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I have 3 8D's in my 38. 1 to crank both Hinos and 2 for house. Was that way when we bought the boat. Worked well and I never changed to anything else. Buy the batteries from our Marina shop. They deliver them, pull the old ones out, then drop the new ones in. I give the two guys 20 bucks each for their help. They call it beer money. I call it awesome!!

I get 5 years out of the house 8D's.

JV

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I hate 8D batteries. Replace with a pair of 27s or 31s? 31 Aug 2017 00:23 #14

  • Norton Rider
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Johnny Vintage wrote: I have 3 8D's in my 38. 1 to crank both Hinos and 2 for house. Was that way when we bought the boat. Worked well and I never changed to anything else. Buy the batteries from our Marina shop. They deliver them, pull the old ones out, then drop the new ones in. I give the two guys 20 bucks each for their help. They call it beer money. I call it awesome!!


LOL... I do the same thing. My mechanic gets Interstate 8D batteries at a super low price. He and his son deliver and install them. I send them Amazon.com gift certificates every Christmas. The reason that I want to get rid of the 8Ds is to lighten the boat a bit and take care of a slight list.

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1999 3788, Cummins 270 "Freedom"
2013 Boston Whaler 130 SS
Anacortes, WA
Last Edit: by Norton Rider.

I hate 8D batteries. Replace with a pair of 27s or 31s? 31 Aug 2017 01:20 #15

  • redskyjoe
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I have twin 315 HP Cummins in my boat. When I bought it last yr it had a single 8D battery to start both engines. When that battery died I replaced it with a single 4D battery just because I didn't want to wrestle an 8D back in there and have had no issues starting the engines. Admittedly, I haven't tried starting the engines in freezing temps so can't comment on the 4D's ability under those conditions.

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I hate 8D batteries. Replace with a pair of 27s or 31s? 31 Aug 2017 13:12 #16

  • Woodsea
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I replaced both 8d wet cell starting batteries with Lifeline AGM group 31 start batteries. One for one. I also disconnected the heaters on the recommendation of Tony Athens and my local Cummins mechanic. They start right up and idle with very little smoke. I'm in warmer water than you folks up north but even in winter (45*) my present setup works great.

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2000 4788 w Cummins 370's, underhulls, swim step hull extension
12' Rendova center console with 40HP Yamaha
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I hate 8D batteries. Replace with a pair of 27s or 31s? 31 Aug 2017 16:14 #17

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Okay, my back is killing me, but I managed to get the dead 8D out last night and installed two 31 Deep Cycles with new boxes in place. I have two more 31s in the truck to replace the other 8D. I'll take some before and after pictures. It will look much cleaner in the lazaret with 31s, as all 4 batteries can fit close together. It looks like there will be a ton more storage space in the lazaret.

The two 31 deep cycles crank my Port Motor as fast as the good 8D start battery on the starboard side (as it should, there are more CCAs available). I'm sure they will crank fine in the winter when the snow is falling, and the pre-heaters should be happier.

I also figure that I can cheat a few amp hours out of these Deep Cycles when at anchor in the summer, by leaving them combined. 4 x 31 is another 480 AH onboard. I might drain the first 25% off them if I don't feel like running the generator to cook breakfast.

Price wise, 4 group 31s Deep Cycles with boxes came out to be just a hair more than two new 8d start batteries.

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1997 Bayliner 4788 "Mostly Harmless"
Sold: 1990 Bayliner 3888

I hate 8D batteries. Replace with a pair of 27s or 31s? 31 Aug 2017 17:43 #18

  • Dooglas
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Seems like two 4Ds would also do the job. Adequate CCA and a heck of a lot lighter than 8Ds. One for each engine, and one can backup the other if necessary.

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2005 Classic 242
5.7L Bravo 2
Portland, OR

I hate 8D batteries. Replace with a pair of 27s or 31s? 01 Sep 2017 03:12 #19

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Cptmorgan wrote: My port 8D start battery is dead. The starboard start 8D is just fine.

I figure I can replace the 8D with a pair of group 27s or 31s for the same price as an 8D, and have a net gain in AH and MCA. Anyone using pairs of 27s or 31s as start batteries?

The Cummins BTAs need at least 1200 MCA in my experience. The preheaters are a battery killer.


the cummins BTA motors are designed for a single G-31 battery... they will do just fine for several years with one battery.
I know people who are using G-27 batts, because they are too cheap to buy the proper G31... but this is not in a boat but in equipment... I am NOT advocating the use of a G27, but a BTA engine requires the same amount of energy to start it no matter what its installed in...

the engines start on about 10amps of power from the battery, even though when you hit the start button the starter may draw 80-120 amps, its only a momentary draw, and after it starts, then the juice is being put back into the battery...
what you need (and may have) are large enough cables for the ground and positive wires from the batt to the engine so that when you hit the start button, there is no amps lost thru heat in the wires as the starter tries to draw what it needs thru them.... I would size the wires according to the distance from the batts to the starter, at no less than 100amps.

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1989 Bayliner 2556, 5.7 OMC Cobra
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I hate 8D batteries. Replace with a pair of 27s or 31s? 01 Sep 2017 22:04 #20

  • cosmo777
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Norton Rider wrote:

cosmo777 wrote: On our 4788 (with 330 Cummins), I pulled out both 8Ds and installed Grp 31's - one for each engine.
Been this way for 2 years without a problem. Pre-heaters stil in place (not unplugged).


Do you boat year round? have you had any problems starting the engines in below freezing temperatures? I realize the water in our area stays between 45 and 50 degrees, but the lazarette will be somewhere in between the outside temperature and the water temperature.

I have had no problems when boating during the winter. Even a week with snow and ice on the docks in the puget sound area for a better part of two weeks

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Pat
Paragon
1999 4788

I hate 8D batteries. Replace with a pair of 27s or 31s? 01 Sep 2017 22:36 #21

  • aluxury1
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Why did you use group 31 deep cycle batteries for starting purposes? You get higher CCA's from start designed batteries.:unsure:

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Brett
2001 Ciera 2858 EC
2007 Mercruiser D'Tronic 250
Sane people, tossing good money into a hole in the water!

I hate 8D batteries. Replace with a pair of 27s or 31s? 12 Sep 2017 00:01 #22

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Attached is a before and after of the STBD lazarette.

I was able to get 4 x 31s in boxes down one side and moved the genset battery out of the way. I suddenly have a ton of storage in the starboard lazarette. Notice a soft spot I found hidden under one of the 8D. I'll need to repair that at a later date.

Engines jump to life with 2x 31 deep cycles each. I suspect a single good quality 31 start battery would be enough as others have shown, but a single 31 deep cycle is not enough based on my experience. I prefer twin deep cycles, especially when you consider that the bilge pumps are wired to the port engine start battery (bet you didn't know that...). Moreover, I could use the weight on the Starboard side...

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1997 Bayliner 4788 "Mostly Harmless"
Sold: 1990 Bayliner 3888
Last Edit: by Cptmorgan.

I hate 8D batteries. Replace with a pair of 27s or 31s? 15 Sep 2017 22:04 #23

  • masonj
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I replaced three 8Ds and 6 6Vs two months ago. The previous batteries were 8 years old. Although the 6 6Vs had a water system, I added a watering system to all of the 8Ds.
So far maintaining the water level in all banks has been an easy event with the watering system. I used a single gallon of distilled water in topping them off each of the past months.
I considered 31s but did not want to change out the wiring systems or risk any limitations in amp capacity.
27/31s would certainly be easier to handle.

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