How to Tell If the Bellows on Your Sterndrive Need Replacing or Repairing

Posted on: 28 August 2017

Before you put your boat away for the season, you should take some time to check the sterndrive for issues. There are a number of elements you may want to check, but this blog in particular looks at the bellows.

Here's an explanation of sterndrive bellows and a few tips on how to tell if these parts have problems.

What Is a Bellow?

In general, a bellow is anything that can be pressed together to release a lot of air. On a boat, a bellow is slightly different. It can be a rubber bit that pushes air or water through part of the boat's sterndrive, but it can also be a rubber covering that keeps water out of the sterndrive. It depends on the type of bellow you are looking at.

What Types of Bellows Are on the Sterndrive?

Generally, there are three different types of bellows on most sterndrives. They are as follows:

  • U-joint bellows—These bellows cover the u-joints. They basically run from the bell housing to the transom plate.

  • Shift Bellows--These run from the transom plate to the shift cable. They protect the boat itself from getting unwanted water in it.

  • Exhaust Bellows--Like the u-joint bellow, this bellow also runs from the bell housing to the transom plate, but unlike the other bellows, it doesn't prevent the intrusion of water. Rather, it pushes water through the drive.

How Do You Tell If You Need New Bellows?

The warning signs vary depending on the type of bellow that is having an issue. However, in general, you should look for the following issues:

  1. Unusual noises when turning the boat indicate issues with the u-joint bellows

  2. Water in the boat that is not from splashes indicates issues with the shift bellows

  3. A noisier than usual exhaust system indicates issues with the exhaust bellows

How Can You Check Your Bellows?

Instead of waiting for the above symptoms to show up, you may be able to find issues by doing a bit of investigative work on your own. In particular, take your boat out on the water and give the sterndrive a work out.

Basically, run the boat at maximum speed and try some sharp turns. If you hear the noises as described above, you may want to contact a sterndrive repair specialist. Let them know that you're worried about the bellows in particular.

You can also do a visual check of the bellows. If the rubber looks cracked or like it's disintegrating, that's also a sign that you may need bellow replacements.