I have this engine and I have not run the boat in a few years, During its sitting I was told the reason it will not start is that the fuel is bad, I understand this but further, the fuel circut in the motor may need some cleaning, I see a fuel filter that appears to be easy enough to drain and frefill with fresh gas and I large silver box on the port side of the motor that appears to have a drain screw in the bottom. I have been told its possible to introduce a fuel additive that will save opening up this thing further and that it should run on the 100 gallons stilll resting in the tank.. Please help with the correct way to get the engine to run again

It has a new battery and turns over with spark just fine