I made a new pipes tonight. These are a full 10 1/2 inches long past the factory exhaust discharge. I also added water brakes on the top and bottom of each pipe. The intrude about 1 inch and are facing towards the rear of the pipe. the bottom is about half way up and the top is 1 1/2 down from where the pipe enters the riser. These should catch any water and turn it around and put it back into the exhaust flow!
Who knows! I'll update later....

im having the same issue with my sbc 5.7, all you did was weld a pipe to extetend the exhaust pipe on the riser so lets out farther down stream? i went thru two sets of new heads because i tuplied no 1 intake and had rust on all the other valves. then decided to get an entire new long block and have carb rebuilt to eliminate any future problems. when i run my engine on the stand i did notice it was wet inside the riser when i looked in.

So far so good with the set up. Ran the boat yesterday for about an hour and no steam issues and no "loading up" when coming off plane. Have a some of carb tuning to do 3200 to 3700 a bit rough but the plugs are dry.

Ran the boat today for another hour or so and running fine. Moved up to 77's on the primary and solved my 3200 to 3700 stumble. Going to 80's to see how she runs.