Can my fuel tank be below my outboard motor?

I have an old sailboat that used to have an inboard motor, but it broke down and I replaced it with a 5hp outboard motor. The old fuel tank sits quite low in one of the side compartments, so that the fuel line starts below the outboard motor and about 3 meters away.

Can I expect some problems using the old tank, or should the fuel pump handle the distance and gravity without any problems? Is it a better idea to place a new tank to the back compartment where it would be closer and above the outboard motor?

A lot depends upon the fuel pump being strong enough. It may not be, or it may simply not last long. Was your inboard also a gasoline engine? Beware of gasoline fumes in the bilge if not!! Even if gravity and proximity make the aft compartment a better place to store fuel, fumes from there can also be explosive. A bilge fan, run for a number of minutes before starting the motor, is an important safety procedure.