Exhaust Flapper & Shutter Service
The Check Valve
for Your Engine.
When you chop the throttle, your own wake can rush up the exhaust pipe. Flappers are the only thing stopping that water from killing your engine.
The "Following Sea"
On stern drive boats, the exhaust sits low in the water. A sudden stop sends a wave of water against the transom. If your flappers are burnt or missing, that water has a clear path to the cylinders.
Silent Burnout
Overheating engines melt these rubber valves. Once melted, they fall down the Y-pipe, blocking exhaust flow and leaving the engine completely unprotected from water intrusion.
Retrieval Service
If your flapper is missing, it didn't just disappear. It's likely stuck lower in the exhaust, causing backpressure. We have the tools to fish out the old pieces and install new ones.
Replacement Protocol.
Accessing the hidden valves deep in the transom.
Access
Depending on the engine model, we either remove the exhaust elbows or, for deeper shutters, remove the drive leg to access the Y-pipe.
Inspect
We check the mounting holes in the Y-pipe. If the old flapper wore through the mounting holes, the pipe itself may need repair.
Install
We install new OEM-spec shutters (often updated designs with better heat resistance) ensuring they swing freely.
Verify
We reassemble the exhaust system with new gaskets and run the boat to ensure no exhaust noise or leaks.
Small Part. Huge Job.
A $20 part protecting a $10,000 engine.
System Knowledge.
We know exactly where they hide on every engine.
Common Questions
How do I know if they are bad?
You often can't see them without disassembly. However, if you hear a loud "clacking" at idle (worn) or if the engine runs hotter than usual (blocked), get them checked.
Can I just run without them?
It is extremely risky. Without shutters, a single rapid deceleration or a large wave hitting the stern while the engine is off can flood your cylinders with saltwater.