The pump was working fine last time out.
the next week I did some main. work and to ckeck th battery strength
I turned the engine over for about 10 seconds without hooking the water flusher.
The next week I came out ,hooked the water and ran the engine -NO water out spout.
I ran it till it hit 180 F and stopped.
Question can the 10 second dry run cause impeller damage?
By "turning the engine over" do you mean you started the engine or simply cranked it? If just cranking you'll not hurt anything. Even running it for 10 seconds won't kill an otherwise good impellor. If the blades were already compromised you could have broken a piece of a vane off and clogged the tube. Could the tell tale simply be clogged? If not and you have no flow, a visual inspection may be the only way to be certain. Was there water coming out with the exhaust?