Kenyon, who had only scored one goal for the Shrimps in two seasons before the game, set his side on their way to a first home win in six games when he stole a march on his marker to head home after 10 minutes.
Kenyon added a second in the 69th minute with a stunning volley. Pompey goalkeeper Paul Jones made a brilliant reflex save to keep out Andy Parrish’s close-range header but the ball fell to Kenyon who let fly with a stinging shot from 12 yards that flew past Jones’ right hand.
The visitors hit back with six minutes left when substitute Conor Chaplin put the finishing touches to a flowing Portsmouth move when he converted Matt Tubbs’ clever through ball from a tight angle.
But Portsmouth’s hopes of a comeback were dashed as Amond scored a third for the home side with one of the goals of the season. The ball was pumped forward and cleared to the edge of the area and Amond produced a stunning left-foot volley which gave Jones no chance as it flew into the top corner.