Replacing Alpha One Your Water Pump (scroll down for Alpha Gen II and Bravo Drives)

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

To remove the 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.
If the water pocket cover looks melted then it should be checked for leaks!

Replacing the 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.
It's easy to pry out and replace if you feel the need to do so.

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 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.

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.

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!
Their 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!

Alpha One Generation II Water Pump Service

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 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.
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 water pump base (Alpha One and R only) has two critical driveshaft seals which go bad so just replace the dam thing.

To remove the 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.

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.
The Seal Carrier is part 807929A1 for $28.85.
Part Number 807929A1 Seal Carrier Alpha Gen II $32.00
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. (Alpha One and R only).
If the water pocket cover looks melted then it should be checked for leaks!

Replacing the Alpha One or R 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 (mentioned above).
It's easy to pry out and replace if you feel the need to do so.

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 water pump base for installation (Alpha and R drives only) 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 (Alpha One and R only).
Slide the base down over the driveshaft and firmly snap it down into place (Alpha One and R only).

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.

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 (Alpha One and R only).

Alpha Gen II's have a special slinger seal. It looks like a double-lipped grommet. The Gen II water pump kit comes with a little slinger seal installation tool. It's really just a small plastic cup. Place the seal over the top of the shaft. Use the cup to slide the seal all the way down. The installation tool installs the seal at the exact correct height. Remove and discard the cup.

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 (Alpha One and R only). This will make it easier to do next year.

READ THIS!
Their 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!

Bravo Water Pump Service

These instructions should only be used as a supplemental guide
to the factory Service Manuals.

The Bravo does not have a water pump in the drive. The Bravo's water pump is mounted on the engine. It is usually down low in the bilge on the front lower starboard side of the engine. The Raw Water pump should be rebuilt every season.

The Bravo Water Pump is belt driven. It has two hoses attached to the rear housing. One hose is the water intake hose and the other feeds to the engine.

The advantage to having the water pump mounted to the engine is that the boat does not have to be hauled to service the pump.

Mercruiser has made some changes to the pump design and method of mounting through the years. Early Raw Water pumps such as those on the old 340 or 7.4L Inboards and TRS model engines used a "clamp-style" bracket which clamped to the nose of the pump. Later styles used a cast bracket to which the pump mounted to on the front side of the pump housing. Later on came the stamped steel brackets which are still used today.

Early fuel injected and carbureted engines mounted the mechanical fuel pump to the side of the water pump housing. If you have a fuel pump mounted to your water pump housing special care must be taken to avoid damage to the fuel lines while servicing the water pump. In short... you will loosen and remove the fuel lines and take the entire water pump assembly off of the engine with the fuel pump still attached. More on this later.

To service the Raw Water Pump it will have to be removed from the engine along with its bracket. It's a fairly easy job although restriction to access can make removal and installation difficult.

Rebuilding your Raw Water Pump Assembly
First remove your boats battery as so the engine won't crank and injure you. I know, it sounds corny but just do it.

Stick your head down into the bilge and take a close look at how the two hoses attach to the back of the water pump rear housing. If you accidentally reverse these hoses when installing the pump, you will ruin your new impellar. Label both hoses and draw the configuration on a note-pad so that when you go to reassemble the pump to the engine you won't get the hoses reversed.

Be aware that if you have the boat in the water that when you remove the hoses from the pump that water might start rushing into the bilge. Never leave the boat once the pump is disconnected unless you have clamped a plug into the intake hose to prevent the boat from sinking.

Look to see if you have a fuel pump mounted to the side of the water pump. If you have a fuel pump mounted to the side of the water pump, you will have to shut off your fuel supply at the fuel tank. Failure to close off your fuel tank could result in damage, injury or death. I know... it sounds corny but just do it. Once your fuel valve is closed and you know that you have already removed the battery from the boat, it is safe to proceed.

Use a good 3/4" Flare Wrench and loosen and remove all the metal fuel lines. This will allow you to remove the water pump with the fuel pump still attached.

The pump is mounted to the engine with one Main Bracket and one Brace. The Main Bracket is mounted to the front face of the pump. It also bolts to the front of the engine block with two bolts. Older Vee-Belt equipped engines had the Main Bracket had a slot in the lower bolt hole which allowed the pump to swivel in and out to tighten the belt. Newer engines with tensioner pulleys and/or Serpentine Belts did not need the slotted Main Bracket.

The Brace is about 1" wide and flat. It bolts to the bottom of the water pump and usually passes under the front of the engine and bolts to the front of the block. This brace gives the pump a little more support. Earlier braces were slotted to allow the pump to swing to adjust and tighten the water pump belt. If the water pump has it's own belt, it will have the slotted Main Bracket and slotted and adjustable lower Brace.

Use a slotted screw driver or a 5/16" nut driver and loosen the hose clamps that hold the large fat thromostat hose in place. Remove the hose. This will give you better access to the Main Bracket's mounting bolts.

READ THIS: The upper Main Bracket bolt may be located just behind the Circulation Water Pump. Depending on what model engine you have, you may or may not be able to remove this bolt without first removing the Circulation Water Pump. The Circulation Water Pump is the wide metal pump bolted to the middle of the front of the block. It is held onto the block with 4 bolts. The upper Main Bracket bolt might just barely clear the Circulation Water Pump. Some do and some don't. I suggest that you try to remove this bolt FIRST. If it won't clear the metal Circulation Water Pump, you will simply have to remove the Circulation Water Pump. No biggie. It comes off pretty easily.

If neccessary, remove the Circulation Water Pump from the front of the block to allow for the removal of the upper Main Bracket bolt.

Use your slotted screw driver or 5/16" nut driver and loosen the clamps to the two water hoses on the back of the Raw Water Pump. Try to pry off the hoses without destroying them. If the boats in the water don't forget to install and secure a plug in the water intake hose. Removing these two hoses from the back of the pump can be difficult. Sometimes it's better to get the pump pulled away from the engine first.

Remove the bolt from the port end of the Brace. This bolt is located on the port front side of the block.

Remove the lower bolt from the Main Bracket and lift the pump out of the bilge.

You should now have the entire Raw Water Pump Assembly along with the Main Bracket and the Brace in your hand.

Go into your garage or shop and grip the pump by the Main Bracket in your large vise with the hose fittings facing straight up. Scribe marks on the pumps housing down to the Main Bracket as so you will be able to align the pump to the Main Bracket during reassembly. Don't clamp the pump itself or the pumps pulley in the vise or you will damage it.

Remove the five screws that hold the rear pump housing to the front pump housing and remove the rear housing assembly. The impellar might come off with the housing, that's OK. Pop the impellar out of the housing and give everything a good inspection.

NOTE: You will not have to disassemble the shaft, bearings and seals from the "nose" housing. Just leave all that together unless you feel the bearings or seals are bad. Refer to the Shop Manual if you decide to rebuild the nose housing.

NOTE: Some changes have been done to the pumps over the years. Older style pumps had multiple layers of parts on the rear of the pump. The old style tended to leak at the gaskets. Mercruiser improved the pump by using a single rear housing section. The new style pumps are less likely to leak and they are easier to build. If you have an older style raw water pump, you will be buying the Raw Water Pump Upgrade Kit. This Kit will replace all the old style multiple layers as so you will have the improved one-piece rear section. The latest pumps which are used on the 496 and MX 6.2L engines are different yet (see image).