It would increase the weight of the boat though, by quite a bit so you'd end up needing a bigger battery. The battery also does not have 100% efficiency so add in another 10% for losses. You'd also need downtime to charge that battery up - about 15-20 hours if you use level 2 charging. Yes, 200 kwh seems oddly low.
Have you seen the massive size of that drum of electric cable on the boat? It weights definitely more than 1200 lb, which is the weight of a Tesla 100 kWh battery. So the boat would be actually more lightweight after replacing that drum with a battery.
