I would not touch the injector pump other than to bleed it if you dont know what your doing. imho
It could be that it was not filled all the way last oil change and what you smell is unburned diesel because of prop, bottom fouling. Maybe you just hooked some rope or fishing line in the prop. Check that first before you start spending money.
That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.