Are you sure you don't have a 2001 Bayliner Trophy? ;>)
7 gallons, but they come in sizes 17 feet to 31 feet and 125HP to 225HP.
2001 Bayliner Trophy Asking Price: $13,999 OR BEST OFFER Condition: Good. Description Location: Ridgewood, New York Seller's Notes: AWESOME BOAT!! Body Style: Power Boat Length: 21 Hull: FIBERGLASS Class: FISH/SKI BOAT Engine: 2010 Hyundai 150 # Engines: one Fuel Capacity: seven gallons Horsepower: 150 VIN: Request the VIN Seller's Comments Great boat, Lots of storage, 270 hours on motor, Well maintained, Reliable, Great for the lake, Depth/Fish/GPS System, Well equipped, Live well, Pump, Anchor, Seats four, Lots of cabin room, Equipped with toilet.
Easiest way is to run it dry with a 1 gallon portable can on board. Stay close to the marina until main tank runs out, top up with the gallon can, and then go to the marina and fill it up. Whatever it takes minus 1 gallon is the capacity. Then refill that gallon can and log how many miles you do on a full tank. I carry 2 x 6 gallon tanks, I know one tank will take my 95 kilometres (I am in Canada)
Red portable fuel marine tanks hold 6 gallons. The size is marked on it. If you have a fixed tank, they are usually 20 gallons, but to be sure use my method and a fill.
Bayliner Trophy 2002