Anything with a 12 to 14 volt, 200 amp output (that doesn’t catch fire or explode) will work. The demand on smaller batteries is proportional to the size and type of starter motor, the the size and compression ratio of the outboard. Newer starter motors in aircraft have rare earth field magnets which are lighter and do not require an electrical input. The Lithium ion batteries have a higher energy density making them smaller, lighter and more expensive. When corners are cut to bring down the cost, they catch fire. There are many options depending on how much you are willing to spend. But be careful what you wish for. . . 😆
