On my '93 there is a set of valves behind the port side compartment door near the transom. If you have 2 motors you will have 2 valves, 1 motor 1 valve. They should have labels "Main" and "Aux" to show you which direction to turn the valve. Not sure if this location holds for all years, but I would guess they will all be in the transom area behind a compartment door.