If you added NOS it would not create more boost. What NOS does it add oxygen in greater volume to the air fuel mix to burn hotter and faster thus making more power. I would not recommend putting it on a boat application. It greatly increases cyl temp and pressure quickly--not something you want in a boat.
Also a bottle does not last that long either and gets expensive to fill all the time. It does work great on a street car though. I had a 150 hp kit on my Chevelle and it took almost two seconds off the 1/4 mile time.