Yes the caps come off. Just some springs above the valves.
When it’s flooded and you shut the mixture screw all the way
the motor should start after a bit and run a little till all the
gas is burned up. Yours doesn’t. The carb has been pretty
much eliminated here. If there is an issue with your carburetor
you won’t know till you can get it to start. Unless there is
some damage, dirt is about the only thing that could give you
a problem. Not much to it.
Tubs.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.