I just installed a 16 gal. fuel tank on my pontoon boat. Always before I used 2 6 gallon Attwood portable tanks and there was usually a little crud left in the bottom. I always dumped it out and started clean. With this big tank I won't be able to do that. The 50hp Merc uses 50/1 fuel mixture and in Missouri the only kind of gasoline I can get is 10% ethanol. I know that ethanol absorbs water, and I always use Sta-bil, and 90 octane gas. I want to add one of those spin-on fuel filters (looks like an oil filter) and this is where my question comes up. Some of them say "Fuel filter" some say "Fuel water separator". I want to do both so do I need 2 of them or is there one that does both?