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Old 07-04-2018, 11:24 AM
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ndutton ndutton is offline
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It's a weakness of a waterlift exhaust system, the risk does not exist with straight pipe, water jacketed or standpipe systems. Waterlifts being IMO the most common exhaust system, the risk is real.

The way a waterlift system works is water injected into the exhaust line is pooled in a container and exhaust pressure pushes it up and out in batches, sort of like a high volume percolator. Where the system fails is when there's no exhaust pressure such as during no-start cranking but the raw water pump continues to deliver water. In time, depending on the volume of the waterlift and rise of the hot section it may be a very short time, water will fill the waterlift and hot section backing up into the engine through open exhaust valves.

Further, as the water builds it exerts greater exhaust backpressure making starting even more problematic.
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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; 07-04-2018 at 11:35 AM.
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