Exhaust Riser

When the boat was purchased, the previous owner was aware that there was a bit of an exhaust leak. We left the cabin open and also opened the forward hatch for ventilation. A carbon monoxide detector was purchased too, but we figured simply operating the engine would be the test for the detector... When I opened up the engine covers with the engine running, we could see the steam rising off the exhaust riser. This had to be one of the first projects to get the boat to a safe, reliable state.

A good friend recommended using PB Blaster to loosen the bolts on the exhaust flange attaching the riser to the manifold on the engine. PB Blaster was also mentioned by name in the Catalina 30 list group. It's GREAT STUFF. I considered myself VERY fortunate to be able to get the riser off without shearing or rounding off either of the two bolts!

Here's a picture of what the riser looked like when it came off the boat:

When we sprayed the PB Blaster on it to remove the bolts, rust was just running off the pipe and bolts. But it at least came off in one part. Once the wrap was cut, the section of pipe leading to the water inlet adapter simply fell away - it was completely eaten through.

Moyer Marine was advised as a source for these parts. I ordered a new flange, new water inlet adapter, and new wrap. (I also went ahead and ordered plug wires, since Moyer had the right ones - but that was un-related to THIS project...) I ordered the flexible rubber exhaust hose to connect the riser to the muffler box from Catalina Direct.

For the pipe - stainless would be nice. But it would also be VERY expensive, and I didn't know anyone in the Austin area that could provide the pipe and weld it. It would also be tricky to get the dimensions EXACTLY right. The local plumbing supply (Crump Plumbing, in Austin) advised galvanized pipe - but I was told that it would give off horrific noxious fumes for the next 2 years. I settled on black pipe pieces from Crump Plumbing to form the bulk of the riser. I also decided to insert an extra elbow to hopefully allow the final fitting to align better with the exhaust box.

So much for best intentions... I got everything put back together with the extra elbow - only to discover that the new setup was too tall to clear the board enclosing the engine compartment. Back to the original configuration. <sigh>

If I remember correctly... I went from the flange, to a 2" nipple, to an elbow, to a 5.5" nipple, to an elbow, to the water injection fitting. The water inlet adapter was attached to the muffler box with flexible exhaust hose.

This was spray painted with the heat resistant paint from Moyer, and then wrapped with two layers of fiberglass exhaust wrapping tape.

Here's what the final result looked like:

In hindsight: The new flange came with a gasket. Since I had to pull the flange back off after the first attempt, some damage to the gasket may have occurred. I used high temp permatex between the gasket and exhaust manifold, but didn't want to risk completely removing the gasket. Not sure if I should have used permatex on both sides of the gasket or not. The amount of exhaust in the cabin when running the motor is tremendously better now. But there was still some steam coming off the assembly, and it appeared to be coming from the flange joint. This may have been due to residue burning off during the first several hours of operation. We'll see...