With a strong following of supporters, there was a good atmosphere at Little Oakley's Memorial Ground.
The young Acorns enjoyed more of the attacking play during the first 45 minutes, forcing a number of dangerous corner kicks to put the Shrimpers under pressure and they deservedly took the lead.
After the break, Harwich got their passing game together to play their best football and the Shrimpers equalised with a goal from Josh Beavis.
With both teams competing well, Harwich's winning goal was really special with the talented Jack Milne (pictured) breaking down the right flank before cutting in and scoring with a classy finish.
There is an early chance for supporters to enjoy the return fixture which takes place at the Gwinnell & Sons Royal Oak on Thursday 30th April, kick off 7.45pm. It will be the Under-18s' final home game of the season.