Mine were cleaned about 2 years ago, just before I bought my 2002 38 Open. I was headed away for vacation on the boat the other day and noticed excessive white smoke out of one exhaust. I turned around and went back to the dock. Called my mechanic. He came out and discovered that both aftercoolers were ruptured. One slightly and one a little more so. I'm not looking forward to the repair bill on this!
I would guess and this is of course without seeing anything, that they MAY have put the wrong O ring on the end plates OR not put together correctly allowing salt water to enter the AC which then caused oxidation from the aluminum housing which then caused expansion and rupture. Take a look at SBMAR.com and boatdiesel.com and you will notice you are not the first for this to happen.