My knowledge of them is that they require special chargers.
My battery drills that have the same batteries but one is ni-cad and the other is lithium won't charge if in the wrong charger...no idea if this is the case with these or not or if an inline adaptor is required.
I don't know about the lithium batteries, but just as a point of comparison, I started a 40 hp yamaha two stroke on my 13 whaler (RIP) for years with just a lawn tractor battery with no problems. You really do not need a battery that will start a v8 truck motor to start a small engine, plus, any weight you save in the back will be a plus. Keep in mind, I did carry a pull start rope, but I never had to use it.
Lots of lithium ion batteries for racing motorcycles are now available. If they will start a 1000cc motorcycle engine, your small outboard is easy. Price is dictated by type of cell used, number of cells and sophistication of battery management system or lack thereof.
Comparisons are also becoming easier as vendors are likely to show CCA and capacity numbers.
Chargers are VERY specific and cheaper batteries without management systems will need a charger to handle that function.
Some of the best and most accurate info can be found here: