You need to get a shop manual first. It's not hard, but nearly impossible w/o a manual if you haven't done it before. If you buy a complete OMC pump kit, instructions are in the box.
If my memory serves, the OMC water pump service kit comes with a full set of instructions on the process...<br /><br />I would still use a service manual durring the process... The Clymer service manual covers all the small details...<br /><br />I know the thought of disassembly of what seems to be half the motor can be a bit daunting, however it's not too bad at all... Once you remove the lower unit, the impeller and pump housing are right on the top.. Remove the bolts and slide the housing and impeller up off the drive shaft...<br /><br />Segments 19 thru 32 of the exploded view link below are the components that make up the water pump assembly.. This is NOT the same gearcase as your 40, but It might give you an idea of the parts you'll be dealing with....<br /><br /> omc gear case exploded view <br /><br /> gear case parts list
