The new system you're referencing is the EPA vapor collection system, similar to what cars have been using for many decades. So, yes, in theory it greatly reduces the amount of ambient air entering the tank and since your tank is plastic, it will suffer less condensation than an aluminum tank will. Will this "eliminate" problems... I wouldn't take THAT to the bank Best practice is still to properly treat the gas with a good additive (which you should really be doing all year) and fill the tank. You can't go wrong doing that and an additive like Startron is pennies a gallon and offers other benefits, too. Is it "needed"? No. But again, it can only help.I was reading an article the other day on winterizing your boat. It mentioned that the new fuel systems do not require storage with a full tank of fuel due to the system does not allow moisture in like the systems of yesterday. I have a ‘18 SPX 210 with Merc 150. Do the new systems truly keep moisture from outside air condensing in your tank or just reduce it? Is a fuel water separator necessary?
I believe the filter that you already have on the engine is a fuel/water separator - although it is quite small. It certainly can't hurt to install a boat-mounted filter - you have plenty of room for it.