New Battery Recommendations Please

royalpiper

Member
Jul 29, 2021
65
Belmar, NJ
Boat Info
1976 Silverton 28 FLYBRIDGE SOLD
1984 Sea Ray SRV 225 Cuddy Cruiser SOLD
2003 Sundancer 260 CURRENT
Engines
Mercruiser 5.0L MPI Bravo 3
2003 260 Sundancer. I'll be replacing both SRM 27 deep cycle Interstate batteries and would like advice on what to replace them with. Stay with the same or other good possibilities?
Thanks in advance.
 
I had the same boat (although doesn't really matter much for this conversation).

How do you use the boat? Do you overnight much? Do you spend lot's of time at anchor during the day without the engine running?

Info on how you use the boat determines recommendations.
 
I had the same boat (although doesn't really matter much for this conversation).

How do you use the boat? Do you overnight much? Do you spend lot's of time at anchor during the day without the engine running?

Info on how you use the boat determines recommendations.
Mostly cocktail cruising for 3 hours or so in the evenings with an occasional overnite trip.
Just running the radio and a set of LED boat drain plug lights while underway. Not a lot of accessories.
 
OK, so running any accessories (other than some crazy setup, maybe) while underway (engine on) doesn't really count/matter. What matters is while the engine is off.

With the occasional overnight trip as the main culprit here, this is what I would recommend (and what I used, as well):

-- A group 24 starting battery
-- A group 27 deep cycle. This will be totally fine for overnights, using some lights, stereo, fridge and Vacuflush.

Use the G24 to start the engine and run. Flip to the G27 when the engine is off and you're using accessories (or overnight). Re-start the engine on the G24.

If you ever need to while you're out, and drain the G27, start the engine on the G24 and then switch over to the G27 to charge it up.
 
If you ever need to while you're out, and drain the G27, start the engine on the G24 and then switch over to the G27 to charge it up.
@Lazy Daze , he needs to be sure he has a battery selector switch that does not fry the alternator diodes switching with the engine running. I think most/many do, but not all.
 
@Lazy Daze , he needs to be sure he has a battery selector switch that does not fry the alternator diodes switching with the engine running. I think most/many do, but not all.
Agree. Yeah, it would be so odd to not have a "make before break" switch that I sometimes don't even bother mentioning that anymore. If he has the original he's good.
 
Do you trailer or wet slip on a charger during the summer?

When it was time I moved up from 27 Flooded to a 31 AGM.

I went to Batteries Plus (10% off if you order online and pick up in store) some have found some deals at Sam's and Costco for the same battery.
 
Check Sams or Costco. I've used them twice and got MANY years out of them. Energizer I think is the sticker on the current ones. The old saying is there's only a couple battery manufacturers and they just add different stickers.
 
If you don’t know why you need different batteries, you don’t. Someone above said it: get batteries that support the way you boat. For example, on the hook all day, blasting your stereo, you might need deep cycle. But rarely will you get longer life out of a different battery. So why pay more if you’re going to replace in about the same time period, unless you have a real reason to pay more.
 
Check Sams or Costco. I've used them twice and got MANY years out of them. Energizer I think is the sticker on the current ones. The old saying is there's only a couple battery manufacturers and they just add different stickers.

Sam's AGM 31's for the last 2 sets of 4 have worked great for me!
 
What kind of charger? No sense in buying expensive AGMs and frying them with a crappy charger.

3 years ago I installed a "ProMariner ProNautic 12 40P". It's taken care of the AGM'S perfectly!
 

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