If it is one with an exhaust
riser and a nipple for the cooling water
from the HX, then most folks make their own out of pipe and have a welder make the nipple. There is somewhere on the internet
that I ran across a pre-made nipple that can easily screw into basic pipe.
Oh, here it is:
NIPPLE from Westerbeke
(courtesy of Dave Mauney, O'Day 35, 1989, "DAMWEGAS" , Oriental, NC , M25XP) http://www.westerbeke.com/SinglePart...f73b1ca82d9219
Sorry, the link appears to no longer work
I got it under parts
, search for exhaust nipple.
For many Catalinas, I know not your boat
Direct makes pre-made riser assemblies.
It appears that you still have the flange on your riser. Make sure you keep that and assure it is in good shape. They're expensive to replace, like around $200.
You might even be able to save the insulation
Here's what some of our guys did:
Exhaust Pipe Replacement - c34.org