Another thought for you - I don't know much about how the 2 HP Yamaha with integral fuel tank works.
Does it have a fuel pump or is it gravity fed?
My guess is gravity fed. If that is the case you are stuck with repairing or replacing the tank. If it DOES happen to have a fuel pump it gives rise to the possibility of plumbing in an external fuel tank like larger outboards use...
(and I just realized that all of us for some reason are replying to this today, when in fact the original post was from 2016!!!
)
The the OP happens to see this it would be interesting to see what he did almost 4 years ago!!!