Both of my raw water strainers work on a suction principle. The are mounted above the water line
. With the top off, they would not work at all. Once the water already in the strainer drained out, the engine would be dry.
Is yours mounted below the waterline?
If you ran the engine for an extended time without water in the pump
, you probably damaged the impeller. The instructor of the engine course I took at Mack Boring recommended coating new impellers with olive oil. This makes them easier to install and keeps them lubed during the initial startup while the pump