As the prop turns, section is created, pulling water through the motor. When first started you would need to speed up the get the water circulating. It’s important that there is no leaks in the system. Its not uncommon to have the solder fail at a fitting or two. I made some new seals using fuel line. Its not likely you can get the water to circulate running it in a barrel.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.
