I voted dual batteries. However, I think dual batteries AND a jump pack.

I have a single, 496 boat with dual batteries. Wouldn't have it any other way. Has come in handy on more than one occasion over the years.

Getting a few things ready before putting her in the water.
To my surprise, the battery switch panel already has 3 switches for Stbd, Port and Parallel plus the posts for jumping a battery. Dual batteries were an option so I guess they just used the same panel. It's a no-brainer.

Current battery is cactus so I'm ditching it. What do I need for a single 496? Will 2 x 70 amp batteries suffice or do I need 76 amp AGM batteries? Easy answer is go the bigger batteries but the smaller ones are local manufacturer and 100 bucks each whereas the bigger ones are imported and nearly 500 each! Are the bigger batteries overkill? Am I just spending money needlessly?

RR

AGM's not needed. What's the CCA of the smaller batteries ?

Any chance you can post some pictures of the engine bay, and the whole boat on the trailer, or in the water ?
I would get 2 of the local AGM marine batteries with the highest CCA rating, and call it a day.
The reason I would get the AGM batteries is that they are maintenance free.
I trailer my boat, and have a battery tender that stays plugged 24/7 when my boat is on the trailer.

I have 2 of the Optima Blue Top D31M in my 27 ZR, mounted in Eddie Marine billet battery boxes. I have been very happy with these so far.

Needed more coffee for me to finally get it. Your statement above in AMPS didn't get thru to me. Now it has. Overseas uses amp/hrs for a rating vs our (US) CCA/MCA .

Not sure on the 8.1's - BUP would know, but I have a Merc Bulletin that states Minimum 150amp/hr for the 454/502EFI engines.
V8 EFI 454 (7.4) V8 EFI 502 (8.2) Min 650 cca or 825 mca or 150 Ah.

For a comparison The 5.7L EFI's require min 120 Ah.
Min 550 cca or 700 mca or 120 Ah.

Fôund that bulletin you referred to and if amps are the same as amp hours, even the little 4 cyl 2.5 and 3.0 liter engines require 90 amp hours so there's no way a 496 would turn over! The electronics guy I'm dealing with supplied new batteries for my last boat and he checked his records, they were 76 amp AGM batteries. That was for Verados and I was told they needed pretty substantial power to start them. Never had a problem.

There must be a different measuring scale. This guy supplies batteries to most of the boats in the marina and he couldn't be that far off. Back in Australia we used CCA as the measure.

Google, hello! Are you there?

RR

@350scarab, haven't put her in the water yet, here's the engine bay and a pic on trailer (probably upside down) taken yesterday.

Could the amps he told me be related to the alternator and a corresponding battery? I notice the alternator output is 65 amps hot and 72 amps cold.

you know as a kid i always thought everything on the other side of the world was upside down . . . now i guess we have proof :D . . . . . go with the big AGM's . . . you can mount them on their side . . . or upside down as it where lol :D


Super sweet ride by the way . . . you gotta be excited to get that thing out on the water :cool: