Tohatsu power units are used in many other makes of small outboards. I once had a similar problem in another make of outboard
. I tried all the usual, carb etc, etc. In my case it turned out to be a faulty ignition suppressor moulded in to the spark plug lead end. The bit that plugs into the top of the spark plug. I simply chopped it off at the lead and from an auto supply I purchased a generic suppressor / connection plug. They screw into the core
of the HT lead. It was an instant fix and cost only a couple of dollars. Worth a try. I sealed the join with some clear silicon.
Another thing to check could be water
in the fuel tank
from rain. Tip out the contents into a container turning the motor
completely upside down. If there is water
clean out the carb as well.