Battery selection

[coreybeck]

I have a Mercruiser 260 in my 89 Carver Montego.

Im being told to replace my batteries by a marine mechanic or "Upgrade" the batteries . He's trying to "upsell" me.

I believe the batteries I currently have in the boat are the specs that Mercruiser suggests.

Can anyone confirm the batteries and specs One should have in the boat or for that engine?

Thanks in advance for your knowledge and opinions!!

[buster53]

It would be nice to know what is in there now? Starting vs deep cell, battery size and age. Are you having any issues now? I assume you only have the 2. No genset with a starting battery?

[Barrett50]

There are only four mfg of auto/marine batts in the US. Exide, East Penn, Northstar, and Johnson Controls. I think all Marine batts are made by one of these four. The Merc 260HP is a chevy 350 engine, so any of the starting engine batts that will work for a Chev will work for starting your Merc. A 24F is a common starting battery.

I use only Duracell from BatteriesPlus as they are warrantied for 3 years pro-rated when installed by a marine mech. Note that marine batts have a vent at the top, and a plastic drain hose, and since about 1981, need to be installed inside a plastic or wood battery tray and secured.

My boat has SIX 8D batts, and I take very good care of them. I'd use a Duracell 24F starting batt, and any of the deep cycle, RV/Marine house batteries that you like. Using a float charger will really extend the life of flooded lead acid batts, and also AGM batts. I would not use an AGM batt in this case except if it was specific for marine application. Also, the charging rate, and charging voltage are different for AGM so the alternator and float charger should be adjusted if changing to AGM.

[Alanna Mo Cree]

QR_BBPOST Using a float charger will really extend the life of flooded lead acid batts, and also AGM batts.

I was recently having a conversation with someone who suggested using a float charger to extend the life of the batteries. If there is already a hard wired charger on the boat, would it help to add a separate float charger? I have been dismissing the idea as unnecessary since the existing charger provides float charging as part of the battery profile, but I'm thinking I might be missing something here.

Apologies for drifting the thread.

[Barrett50]

If there is a hard wired charger, it's most likely allowing the battery to float charge. Knowing the accurate voltage of the batt is important for boats which sit a lot. I use one of these:

https://www.ebay.com/itm/235542665653?_ ... 1J9m&pfm=0

Which has USB connectors, and also the 12V sockets and a digital voltmeter for accurate tracking of batt voltage. It plugs right in to the cigarette socket. The float charge will remain at approx 14.6 volts for flooded batteries. A lot more accurate than the voltmeter on the dash. It draws a small amount of current when plugged in, so only use it when the boat is being used, or when the charger is operating.

[waybomb]

89 Montego, if still had the original charger, you may want to get a newer model. The newer units are much more battery friendly.

[Viper]

For the Merc engine, a 24 group 800 CCA, 1000 MCA starting battery is all you need, and in your case, the flooded lead acid type is just fine unless you want to upgrade for other reasons.

[Barrett50]

QR_BBPOST 89 Montego, if still had the original charger, you may want to get a newer model. The newer units are much more battery friendly.

This is a good point, and is even more relevant in conditions where there is a wide swing in temperature. Modern chargers will have a temp probe to place near the battery that will take the temp into account and keep the charging voltage regulated for different temps in summer and winter.

[Viper]

Agreed. You'll want to put the temp probe on your house/deep cycle bank.

[coreybeck]

QR_BBPOST It would be nice to know what is in there now? Starting vs deep cell, battery size and age. Are you having any issues now? I assume you only have the 2. No genset with a starting battery?

I have 2 X 24 DC 550 (cold cranking) and 685 Marine Amp 12 voltage. with 20 amp charger which Im upgrading.
Ive never had an issue with them but Id like to upgrade the charger as its old