Re: Waterpump impellor change 74 Mercury 20 HP

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Posted by Ed Mc. ( on July 12, 2005 at 08:38:22:

In Reply to: Waterpump impellor change 74 Mercury 20 HP posted by Wayne Lee on July 11, 2005 at 12:59:25:

20 hp has no shift cable or linkage to disconnect. Place the shifter in FWD and leave it there. When the lower unit is down, do not re-position the shift shaft.

If you leave both shifter and shift shaft in place while you're working on the lower unit, the splines on the upper shift rod and the shift shaft in the lower unit should align right up when you reinstall the lower unit.

If they don't, usually all you have to do is 'jiggle' the shift lever a bit until the splines re-couple.

Use a little white grease or other suitable light lube when you install the impeller. Just slather a bit on the blades and wear surfaces on top/botto of the impeller. It helps to put a dab of grease on the impeller key to hold it in place while you're installing the impeller.

Put waterproof grease on the lower unit mounting studs; also some on the rubber water tube grommet. Use a new O-ring on the driveshaft. Lube both the driveshaft and shift shaft but don't get grease on the top of either shaft.

Be sure you have a plastic 'guide tube' installed in the water pump and this tube engages the copper water supply tube in the center section, when you reinstall the lower unit.

When you're reinstalling the lower unit, it helps to slightly turn the flywheel while simultaneously pushing in the lower unit. This'll cause the driveshaft to engage with the crankshaft splines more easily. NOTE: be sure the spark plug wires are disconnected before you start work, to preclude any possibility of the motor starting!!!!


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