I had 2 bad ones one time. Did the same thing as yours. Drove me crazy. Took the junk back to wallyworld and got an OMC line at the dealer. Live and learn.
Tempo and Mercury had a problem awhile back, boo boo in assembly line, some of them had the check valves pointing the wrong way because the person assembling them didn't know there was a difference in direction...you might have picked up one of the old stock....