Checking the exhaust riser on the Catalina 36 MKI

August 9, 2011

What's that black stuff on top of the water lift muffler? Is the exhaust riser disintegrating? If I didn't find out, THAT could be a costly mistake - a corroded mixing elbow or exhaust riser is going to fail at some point and maybe wreck the engine.

Reality Check is 27 years old and the exhaust riser hasn't been touched, it's way overdue. And with a trip to Catalina coming up, I better find out any bad news NOW.

Accessing the exhaust system

The only way to get to the exhaust riser on my 1984 Catalina is to remove the front teak panel in the galley and the shelf in the back berth behind it. Simple, right? Sure, if you know how to go about it.

remove the front teak panel
3 screws in the back and 5 screws in the front

Removing the front teak panel

  1. From the back berth, remove 3 screws holding the front panel on the starboard side.
  2. From the galley, drill out the teak plugs covering 5 screws and remove the screws.
  3. Pull the panel off.
    • It's a very nice tight fit
    • With the front panel off, you can get to the screws holding the back shelf on
remove the back berth shelf
4 screws on the inside of the shelf on the port side, 2 screws on the bottom starboard side

remove the back berth shelf
4 screws on the inside of the shelf on the port side

Removing the back berth shelf

  1. Remove the trim pieces on top of the back berth shelf
  2. From the galley, unscrew the heat exchanger hoses that are held in place on the inside of the back shelf
  3. From the galley, remove 4 screws holding the back berth shelf in place on the port side.
  4. From the back berth, drill out the plugs covering 2 screws and remove the screws holding the shelf in place
    • These screws are on the bottom of the back shelf panel at the sole

exhaust system revealed
Exhaust system revealed

With the exhaust riser revealed you can check everything out.

The hose from the heat exchanger was rubbing against the inside of the back berth shelf on one side and the water injection nipple on the other side. The black stuff on the water lift muffler was from this hose.

heat exchanger hose rubbed
Hose from the heat exchanger rubbed against the back berth shelf

The black on the exhaust riser fiberglass insulation is off of the hose that was rubbing. The fiberglass wrap on the riser lays up against the inside of the back berth shelf - good thing it was really well insulated!

exhaust mixing elbow
Hose rubbed against the exhaust mixing elbow nipple

Nothing was leaking and all the parts felt solid. Sure the riser needs to be replaced, but I figured it was good enough for another Catalina trip - and we were going in less than a week. If a failure does occur I can now get to the exhaust system FAST.

For now, I replaced the hoses and the vented loop that wasn't working. The "Replace The Exhaust Riser" project is on the top of the project list when we get back.

All photos of this project

Checking the exhaust mixing elbow, replacing hoses and vented loop

How did it work out? Did the riser last another trip?

No trouble motoring 30+ hours to and from Catalina on our August trip.

I was glad I had the front panel ready to come off ahead of time though - when I had the engine mounts replaced on a haul out in October the mechanic didn't disconnect the riser and of course it broke. When we got the boat in the water and tried to start it - exhaust and steam! A quick unscrew of the front panel to pop it off and reveal a riser pipe broken. The "Replace The Exhaust Riser" project got moved up from spring to NOW.

Other resources about exhaust risers

  • Here's a great article at that describes exhaust riser issues in detail.

Related topic: Building a new exhaust riser


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