Rebuilding exhaust system for Catalina 30(hot section)

[ajgaines]

Hello! I am the proud owner of a Catalina 30 that has an atomic 4 engine. Somehow water got into the cylinders and oil and I am tearing it apart to get the engine to turn, check the damage, etc etc. When I tried to take the exhaust section off it literally shattered into pieces as the previous owners made one out of something or other that I guess wasn't meant for exhaust...? The bible(moyer manual) says to used galvanized steel or "black steel." Is this just the stuff from home depot? Is there a better place to buy this stuff? It looks like they reused the hot water entry portion as that held up pretty well, but the rest of the exhaust had turned black and will chick away with some metal persuasion.




There is very little space in the Cat 4 to make a big fancy hot exhaust system. In the bible it says to have the water enter 4" above the water lift and have a total of 12" from the top of the exhaust down to the water lift. It looks like the current/past configuration was about 2" and 4" respectively. This would require going up about 12" first as the exit from the exhaust manifold is about level with the entrance to the water lift exhaust. The factory ones sold by Catalina don't come close to meeting these specs. I figure that it is possible to build one and just take out the shelves from the kitchen or something. Should I just go with the like 4" factory setting or rearrange everything/go through the immense hassle of building a 12" one?

[davidsys]

You can build a new CAT 30 exhaust with 1-1/4" Black Iron or Galvanized pipe from you local pipe and supply store, wrapped with fiberglass insulation to keep the heat from the boat hull. You can use an insert section from Moyer, like shown in your picture, or a Black Iron "Y" with a reducer. Space is tight but workable.

David

[joe_db]

Most of our exhausts are built of black iron pipe and do not last forever. I figure replacing mine every 5 years or so.
Galvanized pipe releases a poisonous gas for the first few hours of use from the zinc. It really stinks and gives you an illness called something like "metal fume fever".

[ndutton]

Pictures of my Catalina 30 exhaust project. Please consider 3/8"-16 stainless set screws with washers and hex nuts instead of flange bolts for the attachment to the manifold. The strategy on a Catalina 30 is to get as much rise as possible within the limitations of the galley cabinet. It will never be ideal but we do what we can.

Old black iron pipe and new stainless pipe..Note that the USCG and ABYC require schedule 80 pipe which I would not expect to find at Home Depot.

And the finished stainless pipe installed

[Al Schober]

Two choices on exhaust material - black iron (low cost but on borrowed time after 5 years) or stainless. Don't use galvanized.
Without a waterlift, getting height to the water injection point is the key to satisfactory operation. If you've got room to install the Moyer mixing can, that's ideal (in my book).

[Peter]

"Don't use galvanized"

because it gives off toxic fumes when it is heated

please be safe

Peter

[joe_db]

Originally Posted by Peter

"Don't use galvanized"

because it gives off toxic fumes when it is heated

please be safe

Peter

Metal fume fever is a condition in which the sufferer has influenza type symptoms - a raised temperature, chills, aches and pains, nausea and dizziness. It is caused by exposure to the fume of certain metals - commonly zinc.

[ajgaines]

Originally Posted by ndutton

Pictures of my Catalina 30 exhaust project. Please consider 3/8"-16 stainless set screws with washers and hex nuts instead of flange bolts for the attachment to the manifold. The strategy on a Catalina 30 is to get as much rise as possible within the limitations of the galley cabinet. It will never be ideal but we do what we can.

Old black iron pipe and new stainless pipe..Note that the USCG and ABYC require schedule 80 pipe which I would not expect to find at Home Depot.

Attachment 14430

And the finished stainless pipe installed

Attachment 14431

Thanks for all the helpful responses! So you used stainless for the pipe? Will that last longer than the black iron? I haven't been able to find either at my local hardware store, maybe I need to look further. Do you have any suggestions for the measuring process? It looks like you got yours fitter perfectly, I just have a simple tape measure so I'm not sure I can be that exact..

[jcwright]

Hello Ajgaines.

I've replaced the hot section of my exhaust (on a Tartan 34c) twice over the last 20-odd years, both times with black iron, not stainless. The first time, which was shortly after we bought the boat, everything was seized so I cut the pipe off at the exhaust flange and brought the entire assembly to a local plumbing supply store. They matched all of the sections.

The second time was over 15 years later when I rebuilt the engine. There were no obvious signs of failure, but I don't regret replacing the pipe. The condition of my pipe may be due to the fact that I flush the engine with fresh water after each run. Others with more knowledge may correct me on this. If I had it to do over again, I would probably go with stainless, as did Neil.

best regards,

jack.

[ajgaines]

Thanks Jack! So to recap what you all have said...

Material: #1 is stainless steel, #2 is black iron, #3 and kind of a no-go is galvanized steel.

Size for rebuild in Cat 30: Use what tiny space is between the exhaust manifold and water-lift. I think I will try to raise it maybe .5" above where it currently is as long as it won't be touching the wood above it.

Where to get the supplies: local plumbing store/they can just size and rebuild the old one(but mine was a pretty poor fitting originally.

Thanks for the insights! I have a huge project so I'm sure you will see lots more of my posts.

Cheers