Egyptian forward Marmoush, signed from Eintracht Frankfurt in January, scored his first two goals for City in five minutes.
It took Mikel Arteta’s Gunners just two minutes to open the scoring courtesy of their captain, Martin Odegaard.
West Ham might point to a Mohammed Kudus shot that rattled the post when it was 1-0, but they were never in it.
Chelsea have now gone four points adrift of Liverpool, who can extend the lead to seven points if they beat Leicester City in their game later on Thursday.
Erling Haaland missed a penalty as Manchester City’s torrid run continued with a frustrating 1-1 draw against Everton at the Etihad Stadium.
Liverpool remain top of the table after Chelsea’s goalless draw at Everton.
Kai Havertz then made sure of the victory that lifted Arsenal to the level with leaders Manchester City at 14 points.
Arsenal’s victory extends their impressive winning streak this season. The Gunners are third on the EPL log with two wins in two games.
Leandro Trossard gave Arsenal the lead 20 minutes into the game.
After Ange Postecoglou watched his Spurs side squander a number of chances.
