Agustin Ormaechea also scored for Uruguay, was sent off for two yellow cards and was named the official man of the match in an eventful evening for the scrum-half.
But Fiji had too much pace and power for their amateur opponents, scoring through two penalty tries, Nemia Kenatale, Leone Nakarawa, Tevita Cavubati, Kini Murimurivalu and Nemani Nadolo, who finished with a 17-point haul in front of a record stadium attendance of 30,048.
Fiji lost to England in the opening game - one of three games in 13 days, with defeats to Australia and Wales following - and Uruguay face the already-eliminated hosts in Manchester on Saturday.
Uruguay were the only team in the tournament not to have scored a try prior to the contest.
And, despite the wet ball being the proverbial bar of soap, both sides ran at every opportunity.
Nakarawa's fine offload set up Levani Botia to go over in the corner.
The pass looked forward, but the Television Match Official adjudged Ormaechea to have committed an illegal tackle and a penalty try was awarded, with the scrum-half sent to the sin-bin. Nadolo converted.
Fiji's forwards were dominant, shunting on from a scrum five metres out, with Kenatale simply handing off Duran to score on the blindside.
Alejo Duran kicked a penalty and then hooker Arboleya crashed through the attempted tackle of Dominiko Waqaniburotu to score, sparking jubilant celebrations, not least from Lemoine. Ormaechea converted.
Fiji scored a second penalty try, again converted by Nadolo, after Uruguay's scrum collapsed.
Nadolo, who was suspended for last Thursday's match with Wales, was a destructive force on the left wing.
One Nadolo run was followed by a pass inside to Nakarawa, who showed grace which belied his size to sidestep and dummy his way to a fine try. Nadolo converted.
Fiji were looking for a fifth score, but a long pass went to ground and Uruguay hacked through.
Andres Vilaseca was unable to show the required footballing skills to gather, but Uruguay retained the ball and Ormaechea crashed over. His conversion attempt rebounded off the bar.
Cavubati next charged through to score from close range. The replacement took exception to the Uruguay reaction, sparking a scuffle.
Nadolo again converted before Fiji ran in another from the kick-off, with Murimurivalu completing a move which saw fine interplay between backs and forwards.
Again a skirmish followed and Fiji prop Campese Ma'afu and Ormaechea received yellow cards, ending the Uruguay number nine's game. Nadolo converted once more.
Asaeli Tikoirotuma caught Joaquin Prada and was fortunate not to also be sent to the sin-bin before Nadolo crossed in the corner for Fiji's seventh try.
Matavesi for Volavola (69), Seniloli for Kenatale (62),
Veikoso for Koto Vuli (79), Koroi for Atalifo (80),
Cavubati for Ratuniyarawa (58), Ravai for Waqaniburotu (69),
Talei for Matadigo (57).
Sin Bin: Ma'afu (67).
Tries: Arboleya, Ormaechea. Cons: Ormaechea.
Pens: A. Duran.
Uruguay: Mieres, Gibernau, Prada, A. Vilaseca, Silva, A. Duran,
Ormaechea, Corral, Arboleya, Sagario, S. Vilaseca, Zerbino,
Gaminara, Beer, Nieto.
Replacements: Bulanti for Gibernau (80),
Etcheverry for A. Duran (80), Sanguinetti for Corral (41),
Lamanna for Beer (71).
Not Used: Kessler, O. Duran, Palomeque, De Freitas.
Sin Bin: Ormaechea (3).
Sent Off: Ormaechea (67).
Ref: JP Doyle (RFU).
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