200 HP optimax 2000-no water flowing out

[Tall]

I had a new water pump installed last spring and have used it a couple times since then late last spring. It has set in my shop since. I ran it a couple of times at a minute or so each time but no water flow. I had a hose and muffs hooked to it.

I called the shop that did the repair and he said it may take 4 to 5 minutes. So I started it up again with him on the phone and after a couple minutes nothing, and asked if I idle it up whould help and he said it probably would. I put it in gear and rev it up for another minute or so when an alarm came on and it went in a guardian mode and self went to a idle. So I shut it off. I only have a horn and not the upgraded gauges that read out.

I tried to back blow it with air. Should not be any dirt doppers nest in it. Maybe thermostat problem.

Any suggestions to try to problem solve before I take it to a shop.?