As said, you or a dealer has to do some work, but it can be done. Unless you do a lot of running, the extra fuel isnt necessary. With only 20 gallons I can run approximately 50 miles with a 250 Mercury running hard. Im sure a 200 would get another 20 miles out of that same 20 gallons. Hence, theres 30 gallons under the seat and if you stretched it out you would probably be looking at approximately 90-100 miles or so. Therefore, dont think youll be limited with only 30 gallons of fuel.