The volume of the waterlift should be able to contain all of the normal exhaust hose backwash. The Pearson exhaust system is configured exactly like the Catalina 30 with a couple of significant differences:
- The Pearson has its engine under the cockpit, the Catalina under the dinette meaning the exhaust hose is nearly twice as long and therefore risks a much greater backwash volume.
- The Catalina has far less hot section rise than the Pearson or just about any other boat model on this forum, like maybe 4 inches.
If the Catalina exhaust system can work reliably (I've never had a water incursion) then the observations of the Pearson exhaust should not raise concerns. As for the reports of wakes/following seas finding their way up the exhaust and overwhelming the waterlift, my Catalina has an exhaust thru-hull external flopper and a stainless check valve at the high point of the exhaust hose. Never a problem.
I think we might be getting distracted from the issue in this thread. The engine ran fine as configured for 200 hours then all of a sudden it gets water in the oil without anything changing. Remember, testing has confirmed the water jacket is intact as is the manifold and the original topic of this thread, the head gasket. The exhaust has not been altered - - - YET.