Emlyn Manley Williams’ side completed a festive double over their Anglesey rivals and are now a point behind leaders Holywell Town.
Spurs will be glad to close the gap before three cup fixtures, starting with the Cookson Cup semi-final against Llanrug United on Saturday (1.45pm).
The Harbourmen pressurised the Gwalchmai defence from the start, and it took nine minutes to open the scoring when Mike Kelly hit a looping effort against the woodwork with Gwalchmai keeper Kenny Hughes beaten and Mel McGinness capitalised on a loose ball after Jay Gibbs’ effort was saved.
McGinness nearly made it 2-0 two minutes later, when Gibbs crossed, and the hotshot headed just wide.
The visitors defended desperately as Spurs created numerous openings, with Gibbs shooting just wide with a 35 yard free kick.
It was 2-0 after 35 minutes when McGinness released Gibbs, who ran through to the Gwalchmai area and slotted the ball home past Hughes.
Spurs’ dominance was such that it Gwalchmai 37 minutes to test Holyhead keeper Ben Heald, who saved a Gary Jones free kick.
The second period was much the same and the Harbourmen made it 3-0 on 51 minutes with a McGinness penalty taking his season’s tally to 24.
Gwalchmai spurned chances to hit back, when Gary Jones missed a 74th minute spot kick, and Gareth Allman shot just over three minutes later.
It was all over on 85 minutes when sub Asa Thomas played the ball from the left to Dion Donohue who capped a fine showing for Spurs with their fourth.