Rebuilding exhaust system for Catalina 30(hot section)

[sastanley]

The water incursion happens from an extended crank/no start episode. The impeller in the raw water pump spins with the starter, pushes water thru the engine and out the exhaust pipe at the mixer..since the engine is not running to expel the water from the water lift muffler, it fills up and backs into the hot exhaust section..If the previous owner did not immediately get the water out of the cylinders/crankcase and get the engine running you end up with a frozen engine like you are likely dealing with.

The "fix" is to close the raw water intake valve until the engine is running. But, once it is running move as quickly down to the valve as you can so you don't burn up the impeller from running it dry.

If you get the engine tuned correctly so that it starts fairly quickly (5-10 seconds) you usually don't have to worry about water incursion from cranking. I typically leave my valve closed after the engine has been sitting a long time..she tends to take a little longer on the cranking after a long sit.

[ndutton]

Shawn is, as usual, exactly right. Make your exhaust system as good as it can be within the design limitations of the Catalina 30 and the rest is up to you, how you operate your engine. Your own practices are the real risk.

[sastanley]

Some of that comes from knowing the PO of my boat, and also knowing he did exactly as described..cranked too long, got water in #4, let it sit, had to pull the head, and beat on pistons to get things moving again, and thus lower compression in that cylinder on my engine. I do my best not to repeat.

[ajgaines]

Yes, Cylinder 4 was by far the worst on mine. Then 3 was bad, 2 was just bad-ish, 1 was the only one that looked in good shape