I have a Universal M18 diesel in my 1984 Catalina 27. My exhaust manifold is lying flat and possibly allowing water into the engine in conditions where the boat pitches a bit for a long time. The manifold as show in manuals online is a U-tube with the bottom of the U at the top. At the bottom of the back leg of the U there is a dirt leg and just above that is the junction where cooling water is added to the exhaust. This system makes some sense to me, but my U is lying on its side. When I went to rotate it, I found something rectangular bolted into the engine block, no rotating that. So I think that possibly the U-tube itself must be attached to a fitting that is bolted to the block. The entire manifold is wrapped in the metal mesh/cloth heat protection material as shown in the manuals. I don't want to remove it to check the manifold since it's old and crumbly and I don't want to disturb it unless I have a reasonable chance of finding something useful under it. Can anyone verify what I might expect in there? On another topic, the manuals that were given to me when I recently purchased the boat show an aqualift muffler for all engines. Does anyone know when/why Catalina may have switched?