Word of advice, from the old days. Not much experience with boats, but DITCH the manifolds and get headers, NOW!. The bigger the better where NOS is concerned. Nitrous oxide by itself does not burn. It is an oxidizer, that , when hitting the combusion chamber, vaporizes to nearly pure oxygen, thus enhancing a total burn in the combustion cycle. The bigger the shot, the richer the fuel needs to be to keep from burning exhaust valves, pistons, etc. That's why you have fuel nozzles with the NOS nozzles. It also has a cooling effect of the fuel charge on a hot engine, thereby limiting detonation.
In a nutshell, and THUS, and this is general physics here, if you're burning much more fuel, you need to get the gasses out much more quickly or you'll have a buildup that leads to catastrophic events. This is where you hear of manifolds being blown off or cracked from the stuff.
You have a solid enough foundation for NOS, I would approach cautiously on the size of the shot. 100hp shot, in a boat, to me would seem a monumental increase all things being equal. More that that will likely require an impeller change to realize the crafts new HP curve. Then again, when off the bottle, if the impeller is tailored to when you are on it, performance is going to suffer.
It's a nasty quagmire.
Ray
Ray
