Tuesday, July 19, 2016


Exhaust Leak into the Bilge

On our last trip, I noticed a build up of black water in the bilge. We pumped it out into a container so that I could bring it home and inspect it.

After allowing it to settle for 24 hours, I found that it was salt water (taste test) with black particulate. I believe that it comes from the engine's exhaust system. The engine is cooled by passing sea water through a heat exchanger and then mixing the exhaust with that water which is fed into a 'Muffler' and then the water/air mixture is exhausted out the stern of the boat just above the water line.

The c34.org website is a huge source of info on our boats which were first manufactured 30 years ago. So I turned to the site for advice and there's plenty of it. I'm not the first to have this kind of issue and certainly won't be the last... these boats will be around for at least another 30 years.

So the general consensus is that there is a leak in the exhaust system between the Engine Manifold and the stern. The lack of any telll tale streams beneath the aft berth seems to eliminate a leak at the stern exhaust and in the exhaust hose that goes from the Muffler to the stern. 

The most likely area to fail is the connection of the hoses to the muffler and the muffler hose connections themselves. It could also be the muffler body.

Taking the simplest route first, I decided to replace the hose from the engine exhaust riser to the muffler and while at it inspect both muffler connection tubes for cracks between them and the muffler.

Step 1: Order the replacement hose. 

This hose was from CatalinaDirect.com - they are a great resource for parts for Catalina Yachts.

Step 2: Remove the old hose from the Exhaust riser to the Muffler.
This turned out to be an easy process primarily due to the support that is provided on the Catalina 34 website (http://www.c34.org).
Here's what I did.
  • Disconnected the Hot and Cold supply hoses to the head faucet (after ensuring that the supply was turned off)
  • Disconnected the Engine Raw Water inlet hose from the raw water strainer
  • Moved those 3 hoses out of the way.
  • Used a strip of Gorilla Tape to hold the Head Cupboard Door open by attaching it to the Head Door jamb.
  • Removed all 4 clamps from the Exhaust Inlet to the Muffler and Riser
  • Used my Dremel with Cutting wheel to cut a vertical slot in the Inlet Tube.
  • The hose was Wire Rinforced, the dremel easily cut the wires.
  • The bottom of the hose was too close to the muffler to cut all the way down with the dremel, so I used a knife to open the split all the way down.
  • That made it easy to remove the old hose.

Next it was time to clean up the muffler
The pics shows the Inlet Tube. Possible cracks around the rim of the tube where it reaches the muffler case.

  • Clean up was done using a wire brush, low grit sand paper and solvent. I worked on both the Inlet and the Outlet tubes, they looked a whole lot better after just 10 minutes of labor.
I decided to seal the possible cracks/gaps between the inlet/outlet tubes and the muffler case using Marine Tex a 2 part epoxy. 

After mixing the epoxy and forming into about a 1/4" sausage, I forced it into the joint between the tubes and the muffler case.

Time to let it sit and cure. 


Next step is to install the Hump Hose, but that will have to wait till Friday.

Stay tuned.

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