My 8d starting battery may dead, advice?

[Datenight]

A group 31 replaced the 8-D on the old boat and started the Perkins 6-354 instantly every time.

Rob

 

[Portage_Bay]

If you've got something like this in your engine room Caterpillar D379 Marine Engine you'll want 8Ds. Otherwise smaller with a quality battery charger and save your money and back.

I like the idea of a separate group 31 kept at 100% charge in reserve. Add jumper cables and you're sure to get your engine cranking.

 

[MurrayM]

What about boating and anchoring in below freezing conditions? Wouldn't you want that extra bit of oomph, just in case?

 

[Portage_Bay]

What about boating and anchoring in below freezing conditions? Wouldn't you want that extra bit of oomph, just in case?

Good point. But as others have pointed out a pair of group 31s will give you enough CCAs and be easier on the back than a single 8D.

Another way to think about it is any battery that will reliably fire up your diesel pick up on a freezing morning will spin your yacht's engine just as well. Your engine room won't get as cold overnight as your driveway.

Dyno 12V Starting - 8Dc 1,250 CCA 141 lbs each
Dyno 12V Starting - 31P 700 CCA X 2 = 1,400 CCA 58 lbs each

 

[Art]

IMHO - Boat battery power is rather simple to deal with i.e. conservatively take advantage of; as long as boat owner is not looking to be at head of the class in regard to batt technology. As well, the sooooo many fancy and different-ways/type-apparatus to inter-correlate batt power on a boat are in-and-of themselves complicated... potentially creating repeat problems/breakdowns... besides being expensive at the onset or for replacement.


Don't get me wrong - I'm not speaking of massive yachts that are actually floating mansions. To inter-correlate batt power in mansions can get complicated.


I am speaking of average sized pleasure boats that can accommodate a couple or two with occasional daytime guests. A good gen set with good batt charger [or fuel powered batt charger, or really strong alternator on boat engine] are some of the keep it simple instruments that easily enable days/weeks away from shore power while still maintaining strong battery power.

 

[sdowney717]

I only ever bought one 8D battery and I hated it, yeah super heavy, failed in a couple years, just not for me, never again, waste of cash. It was made by Champion , I had bought from Sam's club. It completely disintegrated on the inside.

 

[dhays]

Another way to think about it is any battery that will reliably fire up your diesel pick up on a freezing morning will spin your yacht's engine just as well. Your engine room won't get as cold overnight as your driveway.

That is an excellent point. Never thought about it that way. Handy for me as my engine is put in a lot of diesel pickups.

I just checked. My Cummins QSB 5.9 engine is used in a number of Dodge trucks as well as RVs etc... They are installed with two Group 34 batteries. Minimum CCA is 750 amps.

Iirc, CCA is the amount that the batteries will put out at zero degrees. In my boat, which is kept in the water year round, I never get close to zero degrees. It seems to me that if Dodge and Cummins think that a couple of group 34 batteries are adequate to start a diesel truck in the winter in the mid-west, then that is way overkill for my boat sitting in relatively warm water.

 

[Nightsky]

What about boating and anchoring in below freezing conditions? Wouldn't you want that extra bit of oomph, just in case?

You definitely would want more battery power under those conditions. Having glow plugs would help in those circumstances.

 

[RCook]

That is an excellent point. Never thought about it that way. Handy for me as my engine is put in a lot of diesel pickups.

I just checked. My Cummins QSB 5.9 engine is used in a number of Dodge trucks as well as RVs etc... They are installed with two Group 34 batteries. Minimum CCA is 750 amps.

Iirc, CCA is the amount that the batteries will put out at zero degrees. In my boat, which is kept in the water year round, I never get close to zero degrees. It seems to me that if Dodge and Cummins think that a couple of group 34 batteries are adequate to start a diesel truck in the winter in the mid-west, then that is way overkill for my boat sitting in relatively warm water.

My Cummins 5.9-powered Dodge pickup sits outside all winter at 4400 feet elevation in Utah, often 10-15 degrees in the morning. A pair of g34 AGM's in parallel has never had any trouble starting it. A pair of g34 AGM's is the start bank for my Volvo KAD44P-powered 26-footer.

For the Nordic Tug's 5.9 Cummins, I replaced an old 4D with a pair of g31 AGM's. They spin it effortlessly.

 

[MurrayM]

Good information about trucks in cold weather, thanks.

The water here never freezes (except in sheltered bays with creeks) so the ocean actually radiates heat into the engine room through the hull, keeping it much warmer than the air outside.

 

[dhays]

For the Nordic Tug's 5.9 Cummins, I replaced an old 4D with a pair of g31 AGM's. They spin it effortlessly.

And if the start batteries are easily accessible, inexpensive LA wet cells would be a very inexpensive alternative.