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A clogged filter creates high head presure on the pump.
Also, when you took an amp reading, it would be better to take it across the fuse [ w/fuse out] so that you get the amp draw of the actual circuit rather than just the pump...this would give you are reading including the wiring and relay parts of the circuit. You were just getting a pump draw reading by bringing power over to pump. The pump is just one part in the circuit that was blowing the fuse.