How to Install a Mercruiser Engine Exhaust Water Shutter

How to Install a Mercruiser Engine Exhaust Water Shutter

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It clatters like a damaged valve shaft when your Mercruiser engine idles, and it makes you hope it's nothing serious. While it doesn't seem as immediately damaging to your engine's health as a seriously bent valve, the water shutter keeps water from backing up the exhaust system and into the engine's cylinders while the engine is running. That clatter means that soon, you'll have to replace the noisy water shutter or face the unpleasant reality of cold water intrusion into a hot engine cylinder.

Items you will need

  • Standard slotted screwdriver

  • Torx driver

  • Water shutter

  • Exhaust elbow O-ring

Step 1

Loosen the small bellows clamp that secures the exhaust bellows to the manifold, using a standard slotted screwdriver. Pull the bellows from the manifold.

Step 2

Remove the three Torx screws from the tabs at the bottom of the upper exhaust pipe assembly, using a Torx driver. Pocket the screws and lock washers for reassembly. The exhaust elbow will pull away from the upper pipe assembly, exposing the water shutter.

Step 3

Lift the water shutter and water shutter retainer from the top of the exhaust elbow. Remove the exhaust elbow O-ring from the exhaust elbow and replace it with a new O-ring.

Step 4

Snap the water shutter out of the water shutter retainer. Snap a new water shutter into place.

Step 5

Lower the water shutter retainer into the top of the exhaust elbow. Drop the Torx screws through their lock washers and the tabs on the bottom of the upper exhaust pipe assembly.

Step 6

Install the exhaust elbow onto the upper exhaust pipe assembly. Tighten the Torx screws securely.

Step 7

Install the small bellows clamp onto the small end of the exhaust bellows. Push the exhaust bellows onto the exhaust manifold. Tighten the bellows clamp securely.


  • The exhaust O-rings are installed dry -- without any adhesive or gasket sealer -- according to the service manual.
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