It's a very good idea to replace your water pump/ impeller in the drive every year.
When your pump fails, engine damage may occur from overheating.
If you have already overheated your engine, then you need to check a few things.
The hot exhaust from an overheated engine will actually melt the upper and lower pump housings.
It will also ruin the seals in the outdrive!!
If you think that your drive might have over heated, it would be a good idea to get it checked out by an authorized Mercruiser Dealer.
What to Expect
Drive work is difficult and messy. The outdrive is heavy so having a friend there to help you lift it off and back on is a good idea.
The best way to replace a pump is to remove the entire drive and have the
drive supported upright in a stand.
You will be required to think ahead about such items as o-rings, sealers and shaft positions.
While the drive is apart.... you need to really inspect everything from top to bottom and inside out.
Place the gear shifter into forward gear.
The shifter MUST be in forward to remove the drive!
Remove the hydraulic cylinders and the six retaining nuts.
Lift the drive by hand a little and let it drop to jar it loose.
It may be stuck so use care to get the drive off!
Support the drive by the lower in an upright position in a stand.
Remove the drain and vent plugs to let the drive oil drain out.
Now you need to unbolt the upper from the lower.
Alpha Ones and Gen 2 drives differ in the fastening hardware.
Most important is to note that a bolt is hidden up under the zinc trim tab.
You must first remove the zinc trim tab and then the screw from underneath.
The Alpha One has two nuts underneath the ventilation plate.
The Gen 2 drive is held together with through-bolts on the sides.
The two side nuts of the Alpha One are the last to be removed and
they will NOT come off all the way until the housings are separated a little.
Sometimes (more than not) the two housings are stuck (corroded) together.
If they are stuck, a thin smooth stiff paint scraper works good to get between the housings at the split.
Once they start to separate then a thicker screw driver will finish the job.
Lift the upper housing off and out of the way. You may notice a little drive oil leaking around.
You should be able to see the pump now.
The Alpha One and "R" pumps have a plastic upper housing and the Gen 2 drives have a Stainless housing.
Remove the housing nuts and/or screws and lift the housing off the shaft.
Remove the impeller, the key and the wear plate.
The Alpha One and the "R" drives have plastic water pump bases.
The water pump base (Alpha One and R only) has two critical driveshaft seals which can perish, its a good idea to replace
these while you are in there
To remove the plastic water pump base, pry up from both sides with two flat screw drives and it should pop right up.
The Gen II does not have a water pump base. It does, however, have a Seal Carrier under the water pump. The Seal Carrier has two oil seals in it which wear out with use. We suggest replacing the Gen II Seal Carrier so the seals stay fresh. The two oil seals are press fitted into the plastic Seal Carrier and the seals are included in the carrier when you buy it.