My plan is to close the valve, disconnect the hose, put the hose end into a pan of water and trying it again. If it works then I have a plugged up through-hull and if it doesn`t then I either have a plugged hose or something is wrong with the head itself. Is that a reasonable plan of action?
Both of our original 1991 Jabsco electric macerator toilets work great, albeit a bit noisy. If your forward head still has the original pump, they're pretty bullet proof. When you fill the bowl with water, does the pump empty the contents into the holding tank? If so, likely a blockage between the through hull and the pump. If it were me, I would disconnect the sea water hose at the toilet, connect a city water hose using an adapter, open the through hull and turn on the city water hose. The city water pressure should clear any blockage (we had that problem several years ago when a fish clogged the aft cabin through hull and died; what a stink. That is how I cleared our sea water line). Once clear, reconnect the sea water hose, pour a gallon of water in to the bowl and try flushing again. It should bring sea water into the bowl. If not, come back to us again for further trouble shooting.
The Jabsco pumps on our boat consist of a sealed motor with a metal impeller and a metal macerator blade on the end that slides into the base of the bowl. If the above steps still do not work, it may be time to remove the motor from the toilet and disassemble and inspect for any loose or damaged parts. It could be that the motor is running, but the impeller and macerator blades are just spinning on the motor shaft, thus unable to prime. If the pump empties the bowl, as I mentioned above, likely that is not the problem. I've never removed the forward head motor, but the aft head I have. That is another story.
Keep in mind, the sea water hose that connects to the toilet is pretty close to the waterline, so wait until you have the city water hose hooked up before opening the through hull valve. On our heads, it does take several seconds of running before the pump brings sea water into the bowl.
P.S. As mentioned by other posters, that is a sewing awl. I've used mine several times over the years. Very handy for small projects. Most of the time I use a waxed nylon twine for sewing canvas and other heavy materials. Regular polyester thread works great for clothing, etc. For those projects, pick up a sewing machine needle, which will fit into the awl chuck. Calling it a Speedy Stitcher is sort of an oxymoron, IMHO.