On a lovely sunny afternoon on an open, grassy Parson Drove pitch, the gusty wind blowing across the Fens and a competitive Drove team made this a tricky assignment for a Harwich squad without key players Louie Bloom, Gareth Heath and Danny Garrad.
Harwich's first chance came after 10 minutes when, from Keelan Milburn's cross, Joe Knight's shot was pushed out by goalkeeper Chris Brazil at the expense of a corner.
Knight was proving to be Harwich's most dangerous attacker and was later the subject of several heavy tackles,
With 35 minutes gone, Harwich took the lead when Alfie Eldridge's cross to the far post was headed home by Knight (pictured).
A scrappy first half ended with Harwich having dug in to remain on top against a Parson Drove team who gave no quarter in their efforts to cause an upset.
With the ball difficult to control, Harwich needed another goal in the second half as a cushion to steady their nerves and allow them to relax.
Milburn had given a good account of himself in the unaccustomed role of a wide attacker and after an hour's play, Shrimpers boss Matt Carmichael replaced him with Luke Mayhew, who was returning from injury.
With 18 minutes remaining, Harwich won a free kick a few yards outside the penalty area, and Brazil did well to push out Mayhew's well-taken effort. Knight was well positioned for this outcome and it seemed that his header would apply the finishing touch, but a goal-line clearance prolonged the tension.
In the closing stages, Parson Drove forced a couple of corner kicks to test Harwich's resolve. It was then that they came closest to snatching a point when young defender Oakley McNair's attempted clearance, caught in the swirling wind, looked likely to finish in the roof of the net, but Shrimpers goalkeeper Brad Cook produced an acrobatic leap to tip the ball over the crossbar.
Perhaps understandably, this was not a great game, but a hard one that Harwich were happy to gain 3 important points from. The victory ensures a top-3 finish - and a home semi-final in the play-offs - and maintains their challenge for second place.
Harwich team: Brad Cook, Alfie Smith (captain), Jack Wood, Dan Keeble, Reece Harte, Tyler Sullivan, Alfie Eldridge, Alfie Canning, Keelan Milburn, Luke Spurling and Joe Knight. Substitutes: Luke Mayhew, Liam White and Oakley McNair (all used).