5 Symptoms To Detect Bad Bellows On Your Boat/Outboard

Are you aware of the bellows designed to protect your boat’s internal components? Like unsung heroes, these small components prevent severe moisture damage, making them vital to your boat’s functionality and level of protection. If your bellows go bad, you will incur a big repair bill sooner or later. 

Then, how could you know if your bellows are bad? Well, like any other components in your boat, there are some common symptoms of bellows that indicate something is wrong with them. For instance, you’ll notice water leaking inside the cabin. 

To some extent, you may experience harsh noise or unusual odors. However, that’s not the end of the story. There are some additional warning signs that you should be aware of. Don’t worry, we have everything described here. 

How Do I Know If My Outboard Bellows Are Bad?

Boats have 3 unique kinds of bellows, which are conventional parts and can be found around the U-joints, shift cable, and exhaust. As a whole, these bellows work to safeguard your boat from major damage. 

No matter which type of bellow is malfunctioning and what’s the distinct symptom, your boat might risk severe damage. 

This is why failing to have your bellows fixed at the right time can flow your extra cash on unexpected and more severe repairs. The following are a few signs that indicate you may require new bellows quickly:

Symptom 1: Leaking Water

While you appreciate that boats should never take on water, you should always check if the cabin has water inside it. 

In case you find water in the cabin, it might be seeping in from a crack or a hole. So, before blaming faulty bellows, it’s advisable to assess the exterior and interior of the vessel. 

First, look at the bilge tube since water can sometimes be taken from that location. Consider checking the surrounding, such as the bow wall of the bilge tube as well.

Keep in mind that if your boat is intended for sailing, plenty of water will flow through the hull. So, you have to seal if there is any crack and clean the bilge completely. 

After that exhaustive inspection, if there’s still water leaking in your vessel, it’s likely a fault with the bellows. 

Symptom 2: Loud Noise

You may hear loud popping or hissing sounds coming from the back of the boat if your bellows are worn out. 

This is a particularly noticeable problem when the U-joint bellows malfunction, and the time you hear it is significantly affected by whether you are turning very slowly or faster. 

Lastly, you may even hear the exhaust making a loud noise. However, these sounds can be described as loud, or they can be either hissing or tapping. 

Symptom 3: Rusting and Dry Rotting

These symptoms are related to leaking water rather than bad bellows. However, since water leakage inside a boat can result from bad bellows, you should be cautious about your bellows when you notice rusting and dry rotting in some components. Here’s how:

  • Rusting

First off, sooner or later, the supporting elements on which bellows sit deteriorate when water and air seep in. 

This eventually leads to rusting. An example of how these parts react to hazardous substances is by rusting. 

Any leakages also lead to rusting the output shaft, as they cause the bearing grease to dissolve. 

A water puddle might also cause water to trickle through the galvanizing grease and keep on rusting the gimbals bearing.

  • Dry Rotting

Dry rot, also known as wood rot, is a specific phenomenon where fungi attack wet, exposed wood. 

The fungal infection occurs when wood repeatedly has been soaked and subsequently dried out. 

When the bellows go bust, a little of the leaking water is absorbed into the interior of the cabin and later evaporated by sunlight. 

If the bad bellows aren’t fixed, you’ll notice dry rotting after a certain period. 

Symptom 4: Unpleasant Odors

This symptom directly indicates something is wrong with your exhaust bellows. When your exhaust bellows are damaged, it can result in exhaust leakage. 

Consequently, a portion of the fuel escapes through the exhaust. You can easily sense the smell of fresh fuel leaking from the exhaust chamber. 

Symptom 5: Boat Sinks

Once again; this is intimately related to the leakage in your boat. In general, the leakage caused as a result of bad bellows might be small. 

Besides, you might not notice the small amount of water seeping through these leaks. 

However, if the bellows are bad and your boat is left in the dock overnight, you may find the boat is sunk completely. When this happens, check the bellows. 

Replacement And Repair Costs Of Outboard Bad bellows

Generally, the only and best way to get rid of bad bellows is to replace them. Based on information from boat owners, the replacement costs of bad bellows and gimbal bearings can range from $1,100 to $1,500. 

However, this can vary depending on the condition of your bellows and whether you’re hiring labor or doing it yourself. 

This is because the replacement cost can be just $500 or less if we cut the labor cost. So, if you are skilled in this area, you can likely save potential expenses. 

You will only have to pay $50 to replace the shift cable bellows, and the cost of the other two bellows is within $100 as well. However, you have to add an extra $100 when replacing the gimbals bearing. 

Here is the breakdown of the cost for different types of bellows summing up the labor cost of $500 as well:

Bellow TypeCostTotal Cost (with Labor)
U-Joint bellow$85 to $100$585-$600
Shift cable bellow$40 to $55$540-$555
Gimbals$90 to $100$590-$600
Exhaust bellow$90 to $110$590-$610

*Note: When you’re approaching to do the replacement on your own, you have to arrange some essential tools and these may cost you around $100 to $150.

Tips For Maintaining The Outboard bellows To Prevent Future Failures

Even if you have replaced your old and damaged bellows with new ones, this is not the end of your duty. Of course, you might not want to see your boat sunk overnight or parts rusting due to bad bellows. 

So, what should you do to prevent future failures? Nothing much difficult; just keep in mind the following tips. 

Ensure Scheduled Maintenance

Bellows are made out of thick, durable rubber. Unfortunately, they do not hold up well over time. As time goes on, the rubber may peel or rip, and water will begin to flow inside. To prevent this, you should maintain these bellows by closely inspecting them on a regular basis. 

Keep the Hub and Bellows Clean

Every time you inspect your bellows, make sure to clean them if there is any dirt, like metal chips, grease, etc.

Replace Other Components If Necessary

Pay attention to the portages, like the water intake, as you examine the leaks. In addition, examine the seals and gaskets and replace them if needed. 

Take Prevention Measures

When repairing the gimbals bearing, you should fluid lubricate it if this part does not readily turn. This way, you’ll never need to worry about rust occurring with this extra protection. 

You should also verify the accuracy of the setup before you replace the drive. A couple of specialized tools will enable you to verify the consistency of the whole setup.


Would you like to learn more about the symptoms related to bad lung health? Perhaps the following section will provide you with something to know. Have a look at the relevant questions and their answers below.

How often should bellows be replaced?

As experts suggest, your bellows should be replaced every two years. However, it’s wise to inspect them annually and replace them if anything seems wrong. 

Can bellows be repaired?

As we have already mentioned, replacing bad bellows is the best and only way to keep your boat free from unexpected damage. This is because the material used to build bellows is hard to repair, and repairing won’t be effective either. 

How do you check the bellows?

Visual inspection is the ideal way to check your bellows. However, this job often requires expertise. You can also check the bellows indirectly. For this, you have to keep your boat at high speed and take sharp turns. If you hear noise, it could be due to faulty bellows. 

Can you replace the bellows yourself?

If you’re skilled enough and confident of replacing your bellows yourself, it’s not anything bad at all. However, it’s good to keep your friend nearby as a helping hand. 

Final Words

Bellows are, for the most part, designed to stay in contact with water. Since the motorized engine can not be immersed in water, the bellows are the only real way to keep it from any damage. 

So if you feel any of the symptoms of bad bellows, you should immediately seek out professional guidance. But, if you’re concerned about having to shell out significant money on repairs, there’s still hope to save your cash. Yes, we’re talking about the DIY replacement again. 

However, rather than saving some cash, regaining performance and ensuring protection to your boat should stay above everything. So, no matter what approach you choose, make sure they’re fixed properly.

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