When singlehanded, somebody grabbing the bow is often helpful when bow on. When trying to get alongside with a fresh breeze taking you off, some help can be essential.
Usually have a plan, and usually works, but often see passers by who would make life much easier if they stopped for a few...
Is there enough electrical grunt at the starter? Doesn't take a great deal of loss of revs sometimes to not start.
Presumably you don't have the water seacock open - just checking.
Manual is here if this is of help - OM 221 20031 HE REV37 0224
There is a wiring diagram which will help in assessing voltage at key switch, and a troubleshooting guide.
As William alludes to, a battery disconnected voltage can hide issues that are evident once you put a load on them (just...
From experience, well worth cleaning the -ve connection onto the engine block.
The voltage on the panel - do you know where that is connected to?. If you have a poor connection or fault then you need to work your way along the system from the battery till you get a low voltage reading - eg...
If mooring next to 5 was an option, and warping across was possible, then sometimes a useful backup plan. Make sure fenders rigged both sides before coming in. Even with no lines attached, once alongside and upwind you probably won't go anywhere, and have the time then to sort things out.
The 'classic' is air getting in the lid of the strainer, which is why I suggested running the engine and filling the strainer manually (with the seacock off). It confirms the 'suck' of the pump is ok.
Putting water into the anti syphon has the possibility of being an unwise move.
Is water filter above waterline? If so, check for air leaks from lid. Is there water in the filter? If not, try shutting seacock and filling it, then starting the engine (lid off) to see if the water is being dragged in by the pump.