Mercruiser Lower Unit Tips at Sterndrives.Com

The U-joint Bellows should be replaced every few years OR
if any leakage or damage is suspected.

Symptoms:
Leaking U-joint bellows will cause severe damage if not tended to immediately.
The two most common symptoms noticed first by customers are water constantly leaking into the boat
and noise coming from the back of the engine/drive area.
It's important to note that once these things are noticed, that some damage has already occurred.
The grumbling noise that so many customers hear is from a rusted gimbal bearing.
The noise will get worse as the drive is turned to full left and full right.
Sometimes a customer will notice water in the drive lube as well.
The front seal of the outdrive is meant to hold OIL in the drive and
is NOT meant to hold water out of the drive.

Inspect the Gimbal Housing Assembly:
With the boat hauled, take a good look at the bellows with the drive
placed in different positions.
Look for barnacle growth, rips and deterioration of the rubber.
The bellows should be clean and firm
A complete inspection will require the removal of the outdrive.
Place the shifter into forward gear and remove the outdrive.
After the rams and the six mounting nuts are removed, the drive should come off. If the bellows have been leaking, the drive might be stuck.
If the drive is stuck, tilt the drive up by hand and let the drive drop back down freely.
The dropping of the drive should free up the driveshaft from the rusted gimbal bearing.
If dropping the drive by gravity still won't free the unit, then some downward "slamming" may be required.

Note: Slamming the drive is a "close-to-last-resort" and MAY damage other components.
Use common sense and maybe a few flat chisels carefully placed to assist in the drives removal.

Be patient and save some money.

Some drives will require a bit of nursing to get off and sometimes the gimbal bearing will
pull right out with the drive!
If it's REALLY stuck, you may have to cut away the bellows and heat the shaft and bearing.
Heating with a torch is VERY dangerous and all precautions need to be taken.
There should be NO GAS in or around the boat. Also, have a hose and fire extinguisher ready.

We have had drives that just won't come off. We call them "junk".

About Tools:
You will need some special and regular tools to do this job.
Without the correct tools, replacing the bellows and gimbal bearing is next to impossible.
You will need:
1. Phillups screw driver.
2. Slotted screw drivers (large and medium).
3. 1/4" ratchet set with extensions and a 5/16" socket.
4. A Mercruiser Hinge Pin tool Part# 91-78310
5. Slide hammer tool Part#91-34569A1
6. Bellows expander tool to install exhaust bellows Part#91-8M0096108.
7. Shift cable socket Part#91-12037 (might not be needed!)
8. Gimbal bearing driver Part#91-32325
9. Driver rod Part# 91-37323
10. Tube of Bellows adhesive Part# 92-86166--1.
11. Dead blow hammer.
12. Perfect Seal sealant.
13. 1/2 long handled ratchet or breaker bar with a 1/2" socket.

Contact mike in our parts department at 954-480-9647 for the parts and tools you need.


Once the drive is removed, a more complete inspection can be done.
Look into the drive shaft hole and notice the inner bellows and gimbal bearing.
The bellows should be dry. This means no oil and no water.
The bearing center should turn smooth with no looseness or binding.
The U-joint assembly should have no rust.

Typically, you will find water, milky oil and rust if the bellows have been leaking.
If you only find drive oil in the bellows, then you have a bad front drive seal which will have to be fixed.

How much can you do yourself?

It depends on the tools and mechanical experience you have.
The transom stuff isn't too bad but if the u-joints are rusted, then you need a Merc tech.

Did I mention we are drive experts? *s* (this "plug" was brought to you by Sterndrives.Com)

Really though, the drive stuff isn't practical for you to do as experience and expensive tools are required.

We can sell you the drive tool set if you would like! It's $2,300 for the Alpha and we will throw in the service manual as well.

OK.... so you feel brave and you splurged for the tools to do the bellows and bearing....let's "do-it".

Disassembly
Turn the steering to one side and remove the trim sender's two screws.
Tie the sender up out of the way.
Turn to the other direction and remove the other trim sender.
Note: If the trim senders are bad, this will be the chance you have to replace them.

Now, take the hinge pin tool with the 1/2" breaker bar and remove both hinge pins.
You will have to turn the steering one direction and then the other to get them out.
Sometimes the pins are stuck. Really stuck. Some heat may be required to free them up.
It may be that you have to actually drill them out!
Drilling is tough and the right size cobalt bits will be needed.
It's important, when drilling, that you don't damage the bellhousing threads!

Now that you have the hinge pins out, take a 1/4" drive 5/16" socket on a long extension
and with a swivel to loosen the bellows clamps.
The bellows should have been glued in place and will require some fuss'n to get them off.
Also remove the exhaust bellows and the water hose clamps.
By now you should have noticed that the shift cable is still attached.
Carefully pull the bellhousing away from the gimbal housing while pulling
some of the extra shift cable though the shift cable bellows.
Note! There should be a small clamp on the small end of the shift cable bellows.
REMOVE THE SMALL CLAMP FIRST!

Now you have great access to the gimbal bearing.
Take your new slide hammer and pull the bearing out.

If the bearing is stuck, you may need to use SAFE heat.
Another little tick is to drill a series of small holes through and all around the aluminum race.
DON'T DRILL INTO THE GIMBAL HOUSING!

I have seen bearings so stuck, that we had to pull the engine and hammer them out from inside the boat.


Cleaning up:
Take the time to clean all the parts before reassembly.
Scrape any barnacles from the transom and bellhousing.
Some sand paper will be needed to clean the areas where the bellows seat.
Look where the gimbal bearing was pressed in. Is there corrosion?
If so, carefully sand the corrosion clean so it's smooth.

Gimbal Bearing installation:
Take the new gimbal bearing and rotate the outer stainless shell
until you can see the hole in the aluminum race.
This grease hole will NEED to line up with the grease passage in the gimbal housing!
I like to mark the bearing with black marker so I can see how the hole needs to line up.

Take some oil or light grease and coat the inside of where the bearing seats and
the outside perimeter of the bearing.
Install your new driver rod onto the bearing driver tool and line the bearing in the housing.
Use a good dead-blow hammer and whack the bearing in STRAIGHT!!!

When the bearing is fully seated, it will make a different hammering noise.

The bearing MUST go in straight. IF it starts to COCK then STOP and pull it back out!!
Take some sand paper and smoothen any burrs that it made.
Regrease and try again.

Once it's cocked, you MUST pull it out or aluminum will build up behind the race.

Now comes the hard part!

Feel the housings where the u-joint bellows are going to seat.
Do you feel the groove?
That groove must be clean and that groove will determine how far the bellows go on.
When installing the bellows..... you will be "feeling" to see if the rim of the bellows seats into that groove.

We need to first install the water hose.
This is where most people give-up.

The water hose is VERY difficult to get in place!

Measure the hose to 13" and cut off any extra.
Make sure you purchased the correct diameter hose!
The hose comes in two sizes, 5/8" and 3/4".

Put the clamp loosely on one end of the hose...real loose......
and put a little soap and water inside the hoses end.

Now, push and twist the hose onto the transom tube.

This will SEEM impossible.

Be patient and keep trying. It is VERY important to get that hose all the way on!
Now that you have killed yourself and you HATE your boat.... we need to attach the other end of the hose to the bellhousing fitting.

The clamp must be properly positioned to face down. Use a 5/16" swivel 1/4" drive socket to tighten the clamps up.

If you completed correctly the last procedure then you should quit your lucrative desk job and become a Mercruiser Mechanic!

So, here you are with bruised knuckles and an attitude to kill.

Put your tools away for the night and get a fresh start in the morning.