After letting the cylinder soak my first attempt was to applying 120 lbs of air.
Second attempt was to fill the cylinder full of paper towels soaked with trans
fluid, blocking the exhaust port, and trying to push it out with grease. Most
likely I had applied heat at some point but I don’t have a clear recollection of
doing that. This motor came from a metal shed with a dirt floor where it had
sat for decades. When the cylinder moved for the first time it sounded like
the crack of an aluminum baseball bat. When tightening the nuts the cylinder
would jump a bit when there was enough pressure. It took several hours to
separate them. The brass rod survived without issue. I expect that once you
get the piston to move it won’t be to difficult to remove, but again don’t try
twisting the piston using the rod.
If this wouldn’t get it out I was going to have to get replacement parts.
If I broke the rod I was going to have to get replacement parts.
If yours is in the same condition as my example, the cylinder it likely
unusable. My piston wasn’t salvageable either. I did reuse the rod.
In any case use, your best judgment.
Tubs
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.