Wow..this could really be serious. Here's one thought. Perhaps water gets in from, say,a passing wake. The boat is tilted more fwd, just enough so the water can't get out, held in part by the flappers. You would think that with flappers it wouldn't get in in the first place but perhaps these are not as good as the hand made ones you built years ago. Perhaps, they are sticking
Is there such a thing as a super size exhaust line check valve????

Re-torque your manifold bolts.
Heat/cool cycles may have loosened them just enough to allow water to seep past gasket.

Boat lists to port with dink.. You did not mention which side of the engine cyl are on that have water in.. one or both rear cyl?

Now if there was prob with the port manifold on your STBD motor.. water would tend to sit on the on the inboard side of the log of manifold while the dink is there. Once removed boat would levels off or may even rest slightly to STB. Water in manifold moves toward the block and leaks into the cyl due to crack or gasket failure? Just a thought


dave

No water in starboard # 7 this time. Not sue why it was there LAST time, but I'm pulling the elbow and riser to take a look anyhow.

Hada bit of an adventure going from my slip to the haul out well to have her pulled for the winter. Just as we approached the well a t-storm--that had been threatening for some time--blew up BIG time! (From blue skies to liquid, roaring, raining hell in ten minutes flat.) I worked the throttles (twin screws) the best I could to avoid hitting pilings, the dock, a party barge, the well timbers, etc. It was all for naught, for the wind--now at 30 mph or more--were in control of my boat and there wasn't a damn thing I could do about it.

The marina guys, now soaked to their skin, secured a line from the bow to lift wellwell, while I got a stern line around a nearby piling. The boat was now secure--though it sidewaysways from lift wellwell. And then we all waited, the drenched marina guys taking a fearsome beating, the motors idling (nicely, thank you), and the wife and I wondering how much damage had been done. (None, mercifully.) . Ten minutes later the storm had passed, the blue sky was back, and we had the boat in the lift well.

What a way to end the season!

Jeff

Awful! Sorry to hear it - but dull days are just that. At least you got a story to tell and it will get even scarier every time you tell it with a little more embellishment (as lightning struck the travel lift...as a waterspout formed just off the bow...as ...) We should have a contest for the next good line.

By contrast, I just ended the season with a finalized sale! Now I have some free time in the spring, Jeff to head north and watch with Millie as you prep the bottom.

OK, there's your answer.
With the dink in place Doc can't get that garden hose up your exhaust.

I read somewhere about some superior flappers that are much more effective.
Sorry I can't be of more help. It seems that when the engine stops with that exhaust valve open and left at the dock... Could some sort of vermin, other than Doc, be crawling up there when the port is underwater?