Re: Tohatsu help
The Tohatsu sounds like an easy fix, per methods described by others above.
The Yamaha is a bit trickier. Beyond the cleanliness of the carb, there are a few tests you can do. The black cylinder sitting atop the carb has two wires. Test this "thermoelectric choke" for resistance with a multimeter; if it reads outside the range of 4.8 - 7.2 ohms it is faulty and will prevent starting altogether (mine read zero but once replaced the 9.9 Yammy fired up perfectly). Another similar test is resistance with the CDI, but you'll need to research the specs. Electromechanical issues like these can be tough to diagnose (I am still learning) but you can do it, sometimes better than the pros.