The Islanders loss was the first the pair of USL-1 clubs suffered in their 12 Champions League games.
Tony Donatelli scored twice and assisted on another goal to push Montreal closer to the CCL quarterfinals. It leads Group C with 10 points (3-0-1) after winning its second straight road match of the group phase. Rocco Placentino and Peter Byers got the other goals for the Impact, which lost, 2-0, to Vancouver last weekend in the second leg of the USL-1 semifinals and went out on aggregate, 2-1.
Joe Public (1-2-1), which beat the Revs 2-1 in Trinidad and 4-0 in New England in the preliminary round, sits bottom of the group with three points and has conceded all three goals that Donatelli has scored in the competition. Placentino redirected a cross from Donatelli to open the scoring in the fourth minute and after Kerry Noray equalized for Joe Public just four minutes later following several fluffed clearances, Montreal took back the lead when Joey Gjertsen set up Donatelli in the 12th minute.
Gjertsen created a crushing third goal just before halftime by getting behind goalkeeper Alejandro Figueroa and squaring a ball for Byers to tap into an empty net.
Donatelli tallied again in the second half after substitute Felix Brillant and Gjertsen unhinged the Joe Public back line yet again. Gjertsen slipped the ball to the ball to Donatelli, who lobbed JPFC keeper Alejandro Figueroa.
In the USL-1 final on Sunday, Vancouver will play Puerto Rico, which rested most of its regulars in Torreón and couldn't contain Mexican champ Santos, which it had beaten, 3-1, during a driving rainstorm in Bayamon two weeks ago.
Oribe Peralta, Andony Hernandez, Agustin Herrera got the goals to end the Islanders' five-game unbeaten streak in the competition. Puerto Rico (2-1-1) has seven points in Group D and shares the lead with Tauro FC of Panama, which after tying CSD Municipal of Guatemala, 2-2, Wednesday has the same record as the Islanders. With its victory Santos (2-2-0) evened its record after losing its last two CCL games and is a point back of the leaders with six.
Puerto Rico went down to 10 men in the 61st minute when forward Joshua Hansen, executing a bicycle kick, instead struck Walter Jiminez in the head and was sent off.
Oribe gave Santos the lead in the 29th minute, Hernandez scored nine minutes into the second half, and Herrera added the third goal with a simple header with 20 minutes remaining.
Group A foes D.C. United (0-0-3) and Deportivo Saprissa (2-0-1) play in San Jose Thursday. The top two finishers in each of four groups advance to the quarterfinals.
In the next round of games, Montreal hosts CD Olimpia of Honduras (1-2-1) Oct. 21 needing only a tie to advance, and Puerto Rico hosts CSD Municipal (0-2-2) Oct. 23.