The 37 year old Rocket Water Pump that is on my 1978 13'
Scamp must be primed with a small amount ofwater before it will pump water.
The "snout" must be removed, and water pored into the top opening of the pump, and then the snout replaced.
I don't know if this is due to it's age, or perhaps it works like several hand pumps I have had on pick-up campers, that had to be primed the first time they were to be used each camping season. After that they worked just fine.
Bill