Re: '56 35HP Evinrude
If it's a '56, it must be a 30 hp. Whether it's a '56 or a '57 ('58?), though, the pressurized tank is critical -- no fuel pump. It sounds like you have a leak in the tank somewhere. Make sure the hoses are tight and that the top assembly (handle, pump, gauge, etc.) is screwed down tight on the gasket. There are kits available to rebuild the tank.