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The Reason That Bellows Are Vital Part for a Boat and How to Maintain Them

What are bellows on a boat?

When you first hear the term, bellows, you may think of something that moves air and gets a fire going. The only connection is the accordion shape of the sides. For boats, it refers to a flexible gasket that protects some engine parts from water. It is typically reinforced for added strength and clamped into place for a watertight seal.

Most vessels have an open-water cooling system as opposed to an automobile which is closed. Instead of antifreeze and a radiator, they use water to keep the craft at a safe temperature by discharging heat generated by the engine. The presence of water within the unit makes some components vulnerable to damage if they get wet. If that happens, you’ll be looking at new boat prices.

Types of Bellows

Bellows have many applications both on and off the water from expandable buses to folding cameras. Their primary purpose is protection from moisture and debris while providing flexibility. Boats have a bellows around the shift cable, one around the U-joints, and another at the exhaust.

Both of these parts are typically impregnated with a pesticide to prevent aquatic wildlife like muskrats from chewing on the rubberized components. A crack in the exhaust bellows won’t sink your boat, but it will fill your bilge and make a mess in the cabin.

You’ll find bellows only on stern drives and not inboards or outboards. Personal watercrafts have one too. The power plant of these vessels consists of two parts, an engine on the transom of the boat and a lower drive unit for steering the craft. You’ll find the bellows in the latter part.

While an inboard uses a rudder, a stern drive changes direction when the lower unit moves when you turn the steering wheel. That’s what makes a part like the bellows necessary. The lower unit can tilt, which makes U-joints vital to allow for the movement. They contain bearings which, in turn, necessitates the watertight protection that the part offers.

Water would damage the bearings and cause them to rust. It’s a costly repair that would have you checking a boat payment calculator to see if you can afford a new craft. Generally, used outboard motors require less maintenance. Nevertheless, you’ll save yourself thousands of dollars if you can take on this repair for your stern drive. If you have a garage and a willing friend to help, it’s a must-do.

How to Know If the Bellows Are Bad

Boats shouldn’t leak. If you find water inside the cabin, there is likely a hole or crack someplace. A loose gasket or clamp may also be responsible. You may notice a loud noise when you’re driving it. That can indicate additional damage involving the gimble bearing and the U-joint bellows. Shifting problems would point to this one. Overheating might mean the exhaust one is bad.

How to Replace the Bellows

A repair involving any of these components is usually expensive. It is time-consuming and hard work since the mechanic has to remove the lower unit to get to the bellows. However, it isn’t difficult, but you will need someone to help you. It is a job for the experienced DIYer. You will need special tools, some of which you can rent at your local auto parts store. You can expect to pay under $100 if you them.

It’s best to replace all the bellows at the same time. After all, they have seen a like amount of wear. The problem rests with the fact that the rubber dries out. They crack from normal usage. And since you’ll have the lower unit off anyway, you might as well do it.

The parts are not outrageous. You can get a shift cable bellows for under $50. The other two will run around $100. You will need adhesive and lubricants specific to the make and model of your boat. Ironically, the time it takes to replace them is less than 30 minutes—after you’ve spent a few hours on the drive.

Removing the Drive

Replacement of these parts is similar. The two are near each other to make the task easier. First, put the boat in the right gear, depending on where the shift is located. If it’s on the right, put it in reverse. Otherwise, it is forward. However, if your boat has two props, you should consult your user manual before proceeding.

Next, remove the prop. The drive is massive and requires two people or a hoist to move it. Having it on the unit makes removal a bit trickier with the added risk of injury, especially if there are sharp edges on from nicks.

You’ll then release the trim cylinder, taking being careful not to let the skeg hit the ground when the drive drops. Remove the bolts securing the outdrive and take off the housing around the exhaust. Turn the unit to the port side for easier access.

Once you free the grounding screw and housing, you can use a hinge pin tool to access the shift cable and get to its bellows. Don’t force them. Instead, use lubricant if necessary. Tie off the trim cylinders to a cleat so that they don’t hang down and risk breaking the hydraulic lines within them. Finally, loosen the bolts securing the drive to the transom.

Exhaust Bellows

You will need to remove the clamps on both ends of the exhaust bellows to replace it. You’ll find it easier if you cut the old one first. Clean the forward mount, followed by adhesive. Then, put the back clamp back in place and use a bellows expander tool to replace the part in the housing. Replace the front clamp, making sure that the screw faces down.

U-Joint Bellows

The process is similar with U-joint bellows. However, you will also need to check and replace the gasket and O-rings too. Use the recommended lubricant from the user manual. Check the housing for rust or debris. You may have to replace the gimble bearing. That means a housing kit that will set you back several hundred dollars.

Shift Cable Bellows

Compared to the previous two, this one is easier if just for the fact that it’s smaller and easier to handle. The setup is similar with two clamps holding it in place. Even if it looks all right, best practices dictate that you should replace it too. Remember that if it goes bad on the water, you’ll have to get this spendy repair or do it yourself again.

Avoiding Future Problems With the Bellows

Once you’ve repaired it once, it’s not as hard to make it a part of your annual maintenance routine. The crucial thing to remember is that prevention is infinitely easier than a tow and repair if something fails on the water.

Take the time to check other parts like the water intake. Inspect all gaskets and O-rings, replacing them as necessary. Lube the gimble bearing if it still spins freely. You can keep it from rusting with this extra layer of protection. You should also check the alignment of the setup before replacing the drive. There is a special tool that can verify that everything is set properly.

Fortunately, many of these tasks are easy to do. Remember that it’s the time getting to these parts that makes the repairs expensive. If you’ve gotten this far, check everything that you can while the boat is off the water and you have the drive off of the boat. The effort you make now will ensure more boating time.