After the visitors struggled to create even a shot in the first half, the Moroccan Bouhaddouz scored their first goal since the end of October with just under 65 minutes played.
A beauty from Sahin at the start of stoppage time completed the victory, condemning interim Fürth coach Janos Radoki to a first defeat in the process.
One change each
In the only change from the side that started at Karlsruhe, the suspended Niko Gießelmann was replaced by Benedikt Kirsch.
St. Pauli are still bottom of the league, and five points adrift of 17th-placed Erzgebirge Aue, but they halted a three-game losing streak with a morale-boosting goalless draw against 1.FC Kaiserslautern last Friday.
Goalkeeper Robin Himmelmann had to be replaced by Philipp Heerwagen in that game with a muscle injury, ruling him out until the New Year, with Heerwagen's inclusion from the beginning here was their only change to the starting line-up.
First half a struggle for both sides
The first chance of an attritional first half fell to the hosts. Khaled Narey crossed in for Mathis Bolly, however he struck into the side netting. Sebastian Heidinger was almost set up by Damjan Djokovic as well, but the ball ran away for a goal kick.
Chances were at an absolute premium for the league’s bottom side as well, and in fact they failed to have a shot on goal in the first 45 minutes. Aziz Bouhaddouz did come close to one, but his chest down in the box got away from him and Balázs Megyeri could clear.
Andreas Hofmann would shoot wide for the Shamrocks, whilst Veton Berisha was correctively given offside after a through ball from Narey.
Sahin almost created a couple more chances St. Pauli before the break too, but the first was intercepted and the second cleared by Kirsch after Richard Neudecker lost control of the ball in the box.
St. Pauli finally taste sweet victory
St. Pauli started the second half brightly, yet it was a defender, Lasse Sobiech, who finally got their first shot of the game. After some head tennis around the box, he volleyed over, but it was a sign that they were growing into the game.
Both sides were trying to ramp up the pressure on each other, with Sercan Sarerer and Kirsch both missing opportunities, but it was the visitors who eventually struck first.
Waldemar Sobota did excellently on the right to keep the ball in play and evade the Fürth defenders, and he eventually crossed to Bouhaddouz. His first shot was blocked, but he was given a second crack, and this time he made no mistake. It was his fourth of the season, and his side’s first since the 1-1 draw with 1. FC Nürnberg on Halloween.
Fürth offered absolutely nothing in response, and it looked like St. Pauli would see the 1-0 win out, but instead they made it two in stoppage time. Zlatko Tripic’s free-kick at the other end of the pitch was headed away by Ryo Miyaichi, with Sahin launching a one-man counter, beating Narey and chipping over Megyeri to complete the long-awaited victory.