The tilt tube on your boat's motor is the hollow tube that the steering cable runs into and through at the motor. It's also the "hinge" that allows your motor to tilt up and down when you use the tilt-and-trim control. You can replace your outboard motor's tilt tube as part of your winter layup, your spring fitting out or as part of your over-the-winter maintenance. While you can replace the tilt tube any time it interferes with your boating activities, the project is not one to be rushed--particularly if you have a large, heavy outboard.
Measure the outside diameter of the tilt tube with a measuring tape. Procure a 12-inch long piece of steel rebar (concrete reinforcing rod, available at hardware stores) of this diameter.
Remove the motor cover of your motor by releasing the cover latch, lifting the back of the cover, tilting the cover forward and lifting the cover free. Set the cover aside. On top of the motor, you will find a "lifting ring." Slip the hook of your outboard motor hoist into the lifting ring and lift the engine sufficiently to take the weight of the engine off of the motor mount, without unbolting the motor mount or removing the motor from the boat.
Remove the nut from the retaining screw that connects the steering link rod (the "L" shaped arm that sits atop the tilt tube and connects the steering cable to the motor) to the end of the steering cable, with an adjustable wrench. Remove the retaining screw.
Pull the steering cable out of the tilt tube. If the tube has internal corrosion that makes the cable difficult to remove, liberally spray a water-excluding lubricant into the tilt tube and wait an hour before removing the cable from the tube.
Set one end of the rebar against the right (starboard) end of the tilt tube and tap the other end of the rebar with a hammer until the tilt tube begins to move. Once you've started the tilt tube moving, begin slipping the new tilt tube in so that as you pull the old tilt tube out, the new tilt tube slides into place. Reconnect the steering cable and reconnect the steering link rod. Lower and disconnect the motor hoist. Replace the motor cover.
Avoid rust and corrosion problems in your tilt tube by replacing the old tilt tube with a new, stainless steel tilt tube.
Your outboard is a heavy piece of equipment. Heavy lifts should always be treated with the utmost respect.