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Outdrive Bellows And Gimbal Bearing Replacement


Bellows Replacement Tips

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


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. Phillips 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#91-45497A1.
  7. Shift cable socket Part#91-12037
  8. Gimbal bearing driver Part#91-32325T
  9. Driver rod Part# 91-37323
  10. Tube of Bellows adhesive Part# 92-86166Q 1.
  11. Dead blow hammer.
  12. Perfect Seal sealant #92-34227 1
  13. 1/2 long handled ratchet or breaker bar with a 1/2" socket.

Shop on-line at 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 the boat owner do? It depends on the tools and mechanical experience. The transom stuff isn't too bad but if the u-joints are rusted, then you need a Merc tech. Really though, the drive stuff isn't practical as expensive tools are required. The drive tool set is $2,300 for the Alpha.

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


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.

Good morning!

Now it's time to glue your u-joint bellows in place. Do NOT install the bellows without bellows adhesive!

It's important to note how the clamps will be positioned The bellows will first be installed on the bellhousing. The clamp will face down opposite the side with the water hose. When we install the bellhousing to the gimbal housing (transom) we will have to have the clamp positioned with the screw facing down on the stb. side.

Now.... note that the bellows has a "Forward" and "up" at one end. This means the obvious!

Coat the "rear" end of the bellows (inside) with bellows adhesive and before the glue dries, push the bellows onto the bellhousing.

It should almost "snap" in place when the grooves line up. Make SURE that they are straight BEFORE the glue dries! Now, position the clamp and gently snug up to tighten.

The next step will be to coat the other end with bellows adhesive and place the clamp loosely on the bellows. Make sure the clamp is positioned with the screw facing down on the right!

Push the entire bellhousing assembly up and into place while feeding the the shift cable back through its bellows. You will have to be feeling inside the hole to assist the bellows into place. Also, you will have to push the bellhousing WAY IN to "snap" the bellows onto the groove. While this is taking place, you also have to watch that the clamp has not fallen out of place!

Once you feel that the bellows are fully in place, hold it there for 5 minutes to let the glue set-up. Now take your 1/4" ratchet set with a long long extension and a swivel 5/16" socket on the end and snug up the clamp. Inspect carefully to make SURE the clamp is straight and in place. DON'T over tighten the clamp!!

Now that both clamps are snug, you can get the hinge pins installed. There should be fiber side washers on either side between the bellhousing and the gimbal ring. If they look worn, replace them. Align the washers and the bellhousing up. Apply a drop of good lock-tight to the hinge pin threads and install the pins.

Torque the pins to 40 lbs and install the senders.

Grease the hinge pin zirt fittings.

Now it's time to inspect your work. Look at the clamps again, are they perfect? Did the bellows seat completely> Is the water hose kinked? If you didn't cut the water hose OR if you didn't get it ALL the way on, then it will kink. It's simple to fix, just redo everything again.

We still have to contend with the exhaust bellows. This is where you get to use your new exhaust bellows expansion tool! This tool will pay for itself with just ONE use. Clamp the exhaust bellows first to the gimbal housing (transom). You really don't need adhesive for the exhaust. The clamp should be on the bottom if possible.

Now place the other clamp on the rear end and get them position CLOSE to the installed position. Work the bellows expansion tool in through the bellhousings exhaust passage and into the bellows. Expand the tool and place the lock in place. Pull on the tool to work the bellows up onto the bellhousing. Now, slide the metal rod pin through the hole in the tool. This allows you to release the tool so you can tilt the bellhousing up to access the last clamp.

Hey! you are practically done! Finish up by properly installing the drive.

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