Timmy, we just sold the bow rider, and we will have to deliver the boat with a battery. Here is a bag of coppers. Take them to the market, and buy the cheapest battery you can find, and hurry back. And Timmy, if you come back with magic beans again you're going to be in big trouble.
The boat dealer is facing two conundrums. First off most smaller boats are not shipped with the batteries. Maybe there is some sort of interstate shipping regulations about this, or tipping the boat just a few degrees will let the batteries tumble out of the marginal restraints used to keep them in place. I think the boat builder just doesn't want to spend the money installing them. This has the added benefit of not testing the boats electrical system before shipping. Why look for trouble in the first place I say?
The dealer has to also worry about whether his staff has the competence and moxie to install the batteries in the first place. I mean look at all of the those wires, and ooh, look at all the pretty colors.
This is the end result. The solution from this dealers cost viewpoint is one cheap battery, with everything plugged into it. It's not hard. Take all the black wires and attach them to the negative post, and all of the reds go to the positive post. Hmm, what about the yellow wire Bob? It seems more reddish, then blackish, and what's up with these pink, and brown wires? It seems brown is closer to black than red. We better call the factory and ask.