Jewmain's lone strike came from the penalty spot, via top-scorer Josh Cohen, to cancel out Sherman's opener but the home side grabbed two more to take the points.
So Fortune sit in second position behind FC Team with a record of nine wins, one draw and three defeats from their 13 fixtures. With five leagues games remaining, plus next week's Division Two Cup quarter-final, Simon Linden's team have everything to play for. Could be an exciting climax ahead.
Reflecting on the match, Linden told JC Sport: "It was a good win and I'm really pleased with the three points against tough opposition.
"It was a very tight game - there was very little in it between the teams and PSJ will feel hard done by with the result. Experience and desire plus Danny Sherman won the game.
"It took a bit of time to get going but in spells we played some good football. We restricted PSJ to long shots and the woodwork saved us on a couple of occasion. It was only a penalty that got past a strong back five, with Ed Bloom in fine form."
FORTUNE: Ed Bloom, Grant Bates, Simon Cohen, Benji Gourgey, Jacob Kalms, Jonathan Kaye, Rob Samuelson, Adam Speck, Liam Stein, Daniel Vandermolen, Danny Sherman. Subs: Michael Goldberg, Josh Lewis, Simon Pocztaruk, Gab Stone
SCORERS: Sherman 2, J. Kalms
PSJ: Daniel Graff, Benji Katz, Alex Landau, Ben Lazarus, Archie Leigh, Gideon Moss, Oli Reback, Alex Rosen, Matthew Stern, Josh Cohen, Zac Summerfield
SCORER: Cohen (pen)
