Re: Had boat hauled, refloated, no raw water flow?
Another possible fault: sometimes the cover plate becomes scored and worn to the point that the pump won't dry prime, but works ok once going. Check the cover plate and if there is visible wear, clean up the outside of the plate with some sandpaper on a flat surface and just turn it over.
Has worked for me a couple of times.
Jim and Ann s/v Insatiable II, reluctantly incarcerated in the POW marina, Hobart, where shore power is assisting our reluctant solar panels in maintaining our life style.