Jeff,

Mine does not have a petcock or valve, it just has a drain plug. I believe it is 1/4 pipe. You should be able to find a replacement valve at most hardware stores, they are usually sold as a gas valve and are brass. You could also use just solid threaded plug.

Try the Catalina Direct web site, I think they have a replacement petcock valve.

The plug method works too. About a year ago, on a day planned for a sail, I had to drain the aqualift muffler. The original petcock came apart.

NOT to be deterred from a great day of sailing, I took a quick trip to WM and bought the correct adapter and plug, since a replacement petcock was not available.

Went sailing after making a quick repair! Didn't even require any duct tape :).

The muffler has a threaded hole that houses the original petcock device. It is a one piece unit, so when the wing nut part broke off, it no longer allowed me to turn it open to let water out.

I was able to unscrew the entire one piece fitting (broken petcock and all) and take it to West Marine to match for size (outer diameter).

I purchased a brass fitting of the correct outer diameter and that exactly screwed into the original hole in the muffler. The fitting has a threaded hole in it. Read on.

I also bought a smaller plug fitting that screws into the hole in the new brass fitting. When I need to drain water, I unscrew the smaller plug, while leaving the larger fitting still securely screwed into the muffler. You just have to use a little care to loosen and remove the small on without allowing the other piece to come out too. Even if it did, it is just water and is not a pressurized system, so there is no big deal.

I cannot recall the exact sizes, but if you have the old one, you just measure and match. IF I can find my receipt, I can tell you the sizes.