Could just be too much gas in the cylinder and its flooded. Take the sparkplug back out and pull the motor over 6 or 8 times to get some air in the cylinder. Put the plug back in, be sure the timing is advanced all the way, and try it again. You should know these motors have a bad reputation and deserve it. While some do run ok, not starting isn’t that unusual with these. I have one that starts easily but runs like crap. The other use to run but now it won’t run at all. They are also fragile. Parts, like the tiller, can easily be broken.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.