Salt water in engine and carb in a pitching sea

[Art Heyman]

Water in engine (aft cylinder) and carb in a pitching sea. Atomic Four in a ’72 Pearson.
I’ve extended the vertical drop of the riser, put a flap on the transom, put a one way valve in the exhaust as close to the bottom of the riser as I can, cut out as much of the exhaust line as possible ( to eliminate trapped water) cut through bulk heads to lower the run of the exhaust line ( again to eliminate trapped water that I ASSUME is being thrown back into the engine ) . I’ve also taken to running her dry for between 5 to 10 seconds prior to cutting the engine off; this seems to help.
I’ve tested the manifold for leaks by blowing smoke into the exhaust line with the carb off.
I installed a water trapping gas filter; water is not coming in from the gas tank.
This does not happen when the boat heals hard to either side, but almost always when she pitches back and forth, as in yesterday in no more than a 2 foot sea.
Someone suggested baffles in the manifold might be corroded – but I don’t know if the A4 was built this way.
Any ideas much appreciated

[Don Moyer]

Art,

You seem to have done a lot of things correctly in improving your exhaust
system, though I'm not a big fan of check valves. Catalina tried a check
valve in their Catalina 30 fleet to compensate for the rather problematic
exhaust systems in those vessels and finally removed the valve as causing
more problems than it solved.

There are no baffles within the manifold but you can pressure-check the
water jacket quite easily by removing the hoses from both ends and blowing
in the front fitting while holding your finger over the aft fitting.
However, your symptoms don't clearly indicate a manifold problem.

Could you post a few digital photos of your system, particularly the hot
section with detail on where the water entry fitting is located?

Don

[msauntry]

How high off the water is your exhaust exit? Does your exhaust run up to the underside of your deck before exiting?

My exhaust exit is only about a foot above water, but I have the hose running up to deck level before it exits. I've had the cockpit swamped from large following waves and never had water back up the exhaust. I've got a Vetus waterlift muffler which helps a little in storing backflow water from the hose.

Could also be your water injection to the hot pipe section of the exhaust. It might be directing water towards your engine somehow instead of down to the muffler.