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Old 11-17-2018, 11:00 PM
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ndutton ndutton is offline
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It is entirely possible your boat never had the check valve. Earlier models did (both Shawn and I have 1977 models) and I understand Catalina dropped them in later model years because they were a constant failure point that caused excessive exhaust backpressure when they failed. Maybe if they used a higher quality valve the failures would not have occurred, the reason I replaced my failed original brass valve with steel flapper pin with an all 316 alloy stainless version. When mine finally quit it was stuck open so I did not have any debilitating symptoms.

What was the point?
For starters, let's accept that Catalina engineer Gerry Douglas knows his stuff. He's not infallible (see lower chainplate failures, plywood shoe in the keel stump, engine harness wiring plugs that dissolve over time) but with the incredible number of boats produced his successes far outnumber the klinkers.

I believe but cannot say for certain the intent of the exhaust check valve was to guard against flooding the waterlift muffler when sailing hard on stbd tack when the entire exhaust line can be below the waterline. Ideally an engine exhaust system is as close to the centerline of the boat as possible so heeling makes little change in the elevations but the Catalina 30's exhaust runs along the port side. This may not mean much to those who sail in light conditions but in my neck of the woods it does. A sail in a 20~25 knot blow may be an exhilarating ride that memories are made of but in Los Angeles outer harbor it might be called Tuesday. It blows like stink every afternoon so a rails under stbd tack is commonplace.

With the external flapper on my exhaust outlet I could probably have done away with the check valve but while I may pontificate on this forum excessively, I'm not about to think I know better than Gerry Douglas. Without good reasoning or experience otherwise, if he thought it was important that's good enough for me. It was installed on my boat from the factory and my engine has never had a water incursion in 41 years so it's my preference to maintain it as originally designed. Note again, that's in my case and sailing in my local conditions.
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Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others

Last edited by ndutton; 11-18-2018 at 03:46 PM. Reason: Add picture
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