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Tools Required to Replace Your Alpha Gen II Water Pump

Unlike the older R, Mr, MC1 and Alpha One drives, the Alpha Generation II drive has a stainless steel water pump housing.
There are special waterpump housing alignment pins required to properly install the housing.
You will need at least two of the special alignment pins although using four pins is best.

No Photo Shown

91-821571A1 Alignment Pins (Used on Alpha Gen II only) $43.00

You will have to drain the lube out of the drive before disassembly which means that
you will have to fill the drive with new lube upon assembly.

To make filling the drive easier Mercruiser sells a handy little Gear Lube Pump Kit.
This Kit/Pump fits into the quart size gear lube bottle and it has a threaded fitting which
you thread into the lower gearhousing drain hole. This makes filling from the bottom-up easy.

802891K2 Gear Lube Pump Kit $12.00 (fits qt size bottles)

As mentioned above, part of the job replacing your Water Pump is changing your drive lube.
There are two types of Mercruiser Gear Lube.
Smaller early model drives such as the R, MC1, MR and Alpha One can all use Mercruiser Premium Gear Lube.
The big TR and TRS sterndrives also used Mercruiser Premium Gear Lube.
Even the new Alpha Gen II Sterndrive can use Premium Gear Lube.
Mercruiser Premium Gear Lube is caramel-brown in color. The Premium Gear Lube works fine and has been proven over the years.
Bravo drives must use Mercruiser High Performance Gear Lube.
This is because Bravo drives have a cone clutch for smooth shifting and this clutch needs that type of lube.
If you have a Bravo One, Bravo Two or a Bravo Three sterndrive you should use Mercruiser High Performance Gear Lube.

NOTE: ALL Mercruiser drives can use Mercruiser High Performance Gear Lube.
The High Performance Gear Lube has excellent properties which makes it ideal for All Mercruiser sterndrive and outboard units.
High Performance Gear Lube is blue-green in color.

NOTE: If your old lube looks bad or if you are changing from Premium to High Performance, make sure to buy a couple of
extra quarts as so you can flush out the old lube.
It is not good to mix lubes although we have never heard of a drive being damaged from doing so.

CAPACITY: 120/140, 888, 470, R, MR, MC1, Alpha One and Alpha One Gen II use about one quart. Buy two quarts.
            Bravo's use about 3 quarts. Buy 4 quarts.
            TR and TRS drives use one gallon. Buy 5 quarts.

92-858058Q01 Premium Gear Lube (qt) $ 17.00 each

92-858064Q01 High Performance Gear Lube (qt) $ 19.00 each

Water Pump Rebuild Kits

The best way to be sure to have all the parts required for a successful water pump service
is to buy a complete Water Pump Rebuild Kit.
The Kits include the housing, stainless cup, gaskets, orings, key, wear plate, impellar and guide tube.
Never replace only the impellar. Never reuse gaskets, wear plates or orings.
While the drive is disassembled you may as well do the job right.

Water Pump Styles
Alpha One customers will typically have the water pump located in the drive.
This pump can be difficult to replace for many boaters.
A good set of tools is a must and having the service manual will certainly help too.

Click Here for complete Mercruiser Raw Water Pumps, Sterndrive Waterpumps and more Pump Kits






If you have a newer Alpha Generation II drive (ser number 0D469859 and up or 1991 and newer)
then you need a Alpha One Generation II water pump kit with the stainless housing.
The Kit is 817275Q05 for $162.00. No base is required.

It is VERY important to know if you have an Alpha One or a pre-alpha / "R" style drive.
If you screw up and try to install the wrong water pump base you can destroy the outdrive.

Some Alpha Ones might not be using the pump in the drive but instead
have elected to use a belt driven sea water pump.
This is usually the case with closed cooling system equipped engines.
Belt Driven Raw Water Pumps are also used on engines with Bravo drives.



The belt driven Mercruiser Raw Water Pump now uses Kit # 46-807151A14 for $128.00

Sterndrive Mounting Gasket Sets

Since most of you will be completely removing the drive to change the water and service the gimbal,
You will need a complete Sterndrive Mounting Gasket Set.
Never reuse the old gasket or orings.
Never use any sealant on the drive mounting gasket.
Always make sure all the surfaces are flat and very clean.

Older Style pre-Alpha One drives (includes 888, 470 and R-type) have an old "crowned" housing design.
Newer Alpha One drives have a modern "squared-off" housing design.
New Alpha Gen II drives also have a squared-off housing but they also have an oil reservoir passage.
Bravo Drives don't use a gasket. They use an Installation Oring Kit.

27-94996T2 Gasket Set $10.00 (fits Alpha One and Alpha Gen II)

It's a very good idea to replace your water pump 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!!

All too many times we see customers replace their water pumps after an overheat only to ruin their outdrives
from an overheated seal leaking out the drive oil.

If you think that your drive might have gotten too hot, have it resealed by an authorized Mercruiser Dealer.

What to Expect
Drive work is difficult and messy. The outdrive is heavy so
if your not in shape then have a mechanic take care of it.

The best way to replace a pump is to remove the entire drive and have the
drive supported upright in a stand.

Trying to replace a water pump without the drive supported in a stand sucks.

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.

Missing one item could lead to drive and/or engine failure. Don't screw up!


Doing It

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 allan head screw from underneath.
Gen II units have a hexhead bolt up under the zinc anode.
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.
That's OK. That's the stinky gross gooey smelly drive oil that loves to get in your hair and clothes.

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.
We strongly recommend that you replace the water pump base!
Why not? Your already here so you may as well do it right.

The Gen II does not have a water pump "base". Instead, it has a Seal Carrier Housing.
You should always replace this plastic Seal Carrier Housing when servicing the Gen II water pump.

The water pump base has two critical driveshaft seals which go bad so just replace the dam thing.

To remove the Alpha One plastic water pump base, pry up from both sides with two flat screw drives and it should pop right up.

Sometimes the bottom round section will stay in the housing. This is screwed up.
If you have done it right, you will see NO PLASTIC left in the housing.

Now is a good time to look things over.
Look down in the water intake passage and make sure it's clean.
Next, flip the upper driveshaft housing upside down and inspect the copper tube and wear it seats.
The copper tube seats up in the "water pocket cover" which has 4 bolts (R, MR, MC1 and Alpha One only).
If the water pocket cover looks melted then it should be checked for leaks!
The Alpha Gen II does NOT have a removable water pocket cover. (A design improvement!)

Replacing the Alpha One water pocket cover sucks BIG TIME because sometimes the bolts snap off
in the upper housing. If they snap off.... you will need a new upper housing!!!

It's very important to inspect the driveshaft where the water pump base seals had been riding.
If the shaft is worn, grooved or pitted, then it should be replaced to prevent water damage.

Read this carefully!
The Alpha and "R" water pump bases are DIFFERENT!
They have different part numbers and will not interchange!
They LOOK almost identical but they are not.
If you have a pre-load pin at the top of the driveshaft, you have an "R" drive.
If you have NO pre-load pin, then you have an Alpha drive.
If you have NO pre-load pin and a stainless housing, then you have an Alpha Gen 2.

The Alpha Gen 2 has no water pump base. Only a plastic Seal Carrier as mentioned above.
It's easy to pry out and replace and it should be replaced when servicing the water pump.

Clean the old gaskets from the housings and clean any other crap that might screw this job up.
It's very important to make sure all the old gaskets and corrosion bits are removed.

Take a can of Mercruiser Perfect Seal Sealant and coat the housing where the gaskets will seat.
Prepare the Alpha One water pump base for installation by first installing the correct gasket on it making sure the water passage hole lines up correctly and then choose the correct o-ring that fits around the round part in the groove.

Coat the o-ring with Perfect Seal.

Take some Mercury Marine Special Lube 101 and fill between the two seals in the pump base.
Slide the base down over the driveshaft and firmly snap it down into place.

Gen II customers should fill the gap between the two carrier seals with special lube before installation. Coat the carrier orings with Perfect seal. Be sure to use a suitable tool to lightly tap the seal carrier down into the housing. Now you need to get your act together on how the upper gaskets fit on either side of the wear plate.
Take your time and familiarize yourself with how they fit.
After you have figured it out, slide the first gasket, the wear plate and the second gasket down.

Now you need to remember to place the water pump impeller key in place!
Hold the key in place while you slide the impeller down over it.

Gen II customers need to install two or more water pump housing Alignment Pins into the housing bolt holes.

Take some Special Lube 101 and grease the inside of the water pump housing cup.
As you lower the water pump housing in place, turn the driveshaft clockwise.

Make sure you use the correct washers and mounting nuts.
DON'T over tighten the nuts!!!!
If you over tighten the nuts you will ruin the water pump.

Install the plastic guide tube making sure the rubber grommet is in there first.
Slide the square looking o-ring slinger seal down the driveshaft till it hits the pump housing.

Older driveshafts have a groove at the top for the upper o-ring. Install the o-ring if used.

Grease up all the studs on both drive housing halves. This will make it easier to do next year.

READ THIS!
There is a "quad seal" that MUST be installed at the oil passage gallery.
If you forget this quad seal, the drive will blow up on its first use.
Also... there needs to be a flat washer installed over the small shift shaft (Alpha One and R only).
If you forget to put the washer in place, the shift shaft will drop and
you will loose shifting at the worst time. The Gen II does not have this washer on the shift shaft.
Also.... Don't forget to have the zinc bolt in place before mating the housings together!

READ THIS TOO!
The drive lower and upper shift shafts MUST be in forward position before mating!
Put the lower in forward gear by turn the shift shaft clockwise and locking the prop shaft in the reverse direction.
Once its in forward... don't bump it!
If you bump the prop, it will knock it out of forward!
Ok... you have the lower in forward... now place the upper shift shaft in forward as well.
The upper shift shaft must face fore and aft. That's forward!

Lower the upper driveshaft housing into place making sure to align the copper tube into the plastic guide tube.

Did you knock the thing out of forward? Check it!
Turn the u-joints so the splines line up and the upper will fall into place.
You must FIRST separate the housings just enough to get the side nuts on!
After both side nuts are installed, then instal the front nut, the two underneath,
the allen under the zinc and snug them all up.
It's a good idea to check your shifting before going any further.
In forward.... the brass shift rod will face fore and aft.

Now.... get a pressure testing pump and pressure test the drive to 15 PSI.
If you don't pressure test the drive then don't cry when oil leaks out.

You really really need to pressure test the drive. Trust me on this.

Fill the drive with Mercruiser Drive oil from the bottom until it overflows
out of the upper side vent plug hole.

Make sure the drain plugs have perfect gaskets and are snugged up tight.

Place the new drive gasket and all the new mounting o-rings in place.
Check to see that the shifter is in forward and that
the drive is also in forward and install the drive.

Test run on a garden hose with a good flushett before launching.

It's a good idea to recheck the drive oil after the first use!



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