Victories over Vitoria Setubal and Estoril had given the club a perfect start to the new campaign.
And that continued in front of their Estadio do Rio Ave Futebol Clube fans on Sunday, Renan Bressan putting his side ahead in the 26th minute.
The home side pushed for another and grabbed it almost immediately through Diego Lopes.
Rio Ave's cause was benefitted by a second yellow card for Boavista defender Lucas in the 59th minute.
And the gloss was added by two late goals, Esmael Goncalves and Emmanuel Boateng sealing a comfortable triumph against the visitors' 10 men.
Rio Ave finished 11th in the table last season, yet currently top the pile in Portugal's first division.
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