The impeller on the water pump of your Tohatsu 40-horsepower engine is used to help pull water into the engine to keep it cool. Over time, constant use can cause your impeller to be damaged and to break down, which will cause the engine to overheat. To remedy this problem, you need to replace the impeller as soon as it becomes damaged. The job will take you the best part of two hours to complete.
Place a drain pan underneath the outdrive, which is below the upper unit. Use a flat-head screwdriver to remove the screw attached to the drain plug at the bottom of the outdrive. Remove the plug and drain the gear lube into the pan.
Use a socket wrench to remove the bolts attached to the outdrive. Remove the outdrive from the upper unit and move it to a clear work area.
Remove the bolts attached to the water pump housing on the side of the outdrive, using a wrench. Lift the housing away from the outdrive.
Slide the water pump impeller away from the spindle and replace it with a new one. Place the water pump housing back on the outdrive and secure it with the mounting bolts. Lift the outdrive back up to the upper unit and secure it in place with the socket wrench.
Attach a gear lube insertion tube onto the drain hole of the outdrive. Pump gear lube into the outdrive. Reattach the drain plug once the outdrive is full.
