Seamer beat Scalby 3-0 at the Flamingo Land Stadium on Wednesday night to set up a Scarborough FA District Cup final clash with West Pier.
After an end-to-end opening 25 minutes, Danny Glendinning latched onto the end of a low cross to fire Seamer into the lead.
Scalby almost levelled five minutes later, Harry Holden hacking off the line after Brad Smith had lobbed the keeper.
Glendinning netted a fortuitous second on 35 minutes, his initial effort coming back off the impressive Scalby gloveman Max Tadman and deflecting off him into the net.
Seamer struck the bar just after the break, Kris Tate's long-range strike crashing back off the upright.
The scoring was completed on 55 minutes, Glendinning lashing in from the penalty spot to compete his hat-trick and the victory after referee Mick O'Brien spotted a foul in the box from a Seamer corner.
Seamer were good value for their win, spurning several chances and being caught offside numerous times, while Tadman frustrated them on at least eight occasions.
Centre-back Danny Price was solid for the victors, who were comfortable throughout, while Tadman and Darren Swinger were Scalby's stand-out players.
Tommy Adams' side will now take on West Pier in the final, after Andy Spivey's men beat Edgehill in their semi-final.
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