I'd go with the second battery. Especially since you said it was an option, already a place for it. Play the stereo during the day and be able to flip it. Not to mention if you happen to break a cell in the battery, may be a chance even with a jump box that the EFI will not fire. You can get a great second battery for about a 100 bucks. That's cheap for piece of mind. Just my thoughts.

I'd like this post, but ya know... Yes, the 496 needs lots of juice to start. I got stranded one time last year and couldn't even get it to fire off good quality jumper cables from a running boat next to me. It turned over fast enough to start, but not enough juice to fire. I understand liking the clean look, but a 2nd battery is the way to go.

I'd give a thumbs up but its no longer an option...lol

I'd go with a second battery. I probably would install it on the starboard side also to counteract any prop torque.

OK , my .02c
Magnum 25 , single 502 , 2 x 27 series batteries . One port , one stbd , like they SHOULD be .
If , by chance , you're in the water permanently the Mercathode constantly drains the battery it's hard wired to .
Solution , a mini solar panel charger wired to that battery that quickly disconnects for when you want to head out . If you trailer pull the fuse for the Mercathode when you're on land .
IMO hauling a booster pack in and out all the time is more inconvenient than permanently hooking up a 2nd battery and the suitable battery switch once and for all .

Tesla now makes solar shingles, see if they can make a solar Faring

Good responses, thank you all. I was hoping for a one-sided argument but the opinions are mixed.
I'll never overnight on the boat, it's only a basic stereo to power when at anchor for a couple of hours, think I might just keep track of the for v against posts and go with the numbers.

@DBleil, avatar updated. :

RR

I vote for the second battery option, I just had to be towed back because 45 minutes from home my only battery decided not to hold a charge. The motor would turn over fine and idle fine but once I tried to get on plane it would fall on its face.

You dual battery folks are nuts. They weigh the boat down and lose both handling and speed all for what? Batteries such as glass mat are totally faithful for years and years. Carry a set of jumper cables and call it a day.

Should have done it to start, I've added an anonymous poll, please vote, there's more relevant knowledge on here than in the whole of Thailand.
BTW, I ain't voting!