"It was a big series," Iwakuma said through translator Antony Suzuki. "Winning the first two of the three was big and I needed to finish up the series strong. I was very excited from the beginning and I'm very happy with the win."
Mariners pitchers have now allowed three or fewer runs in a club record 12 straight games, which ties for the second-longest such streak by an AL team since 2000 (the Royals had a 13-game run in 2013).
Toronto came into the series tied with Seattle, but wound up being outscored 19-4 despite having the third-highest scoring offense in the league.
"They shut down our offense, stone cold," said Blue Jays skipper John Gibbons. "We scored a few last night, but it was pretty much a mismatch. They get to the 'pen, and there's no let up down there either."
The 8-1 mark ties for the second-best homestand of at least seven games in Mariners history, behind only an 11-1 run in 2001. Seattle also went 8-1 in a 2012 homestand. There have been 224 homestands of seven or more games in franchise history.
Iwakuma came into the game ranked eighth in the AL in ERA, third in WHIP and first in strikeout-to-walk ratio and he did nothing to hurt those numbers in a 101-pitch outing in which he walked one with five strikeouts. After missing the first month with a strained finger tendon, the 33-year-old has grown increasingly effective in the past six weeks and is 6-2 with a 1.83 ERA with four walks and 54 strikeouts in nine starts since July 1.
Relievers Charlie Furbush, Danny Farquhar, Yoervis Medina and Fernando Rodney finished off the shutout for Seattle, with Rodney racking up his 35th save to move back into a tie for the league lead with the Royals' Greg Holland.
Pitching has carried the Mariners all season and they lowered their AL-leading ERA to 2.95 with their eighth shutout of the season.
"Heck, tonight a two-run home run in the first is all it took," said catcher Mike Zunino. "It's incredible. Our starters and our relievers, I feel like, are the best in baseball. We feel like we have a lead and we have confidence. Obviously we always want to tack on more, but it's just something where we [get] a little extra boost when they're out there."
Morales supplied all the offense that was needed as he continued his recent surge with an arching two-run blast into the right-field seats off knuckleballer R.A. Dickey in the first inning. It was Morales' second home run in as many nights after not going deep in his first 16 games with the Mariners following his acquisition from the Twins.
"He just left it up and I was able to connect well," Morales said through interpreter Fernando Alcala. "I've hit against him in the past and it's not easy."
"I thought it was a good knuckleball," said Dickey. "I tried to elevate one to get him to swing through it and he tomahawked it out. I have to tip my hat. But outside of that I felt like I battled pretty good tonight."
Morales went 2-for-3 with a walk, raising his average to .206 with Seattle and .225 on the season. He has shown signs of breaking out in the last five games, hitting .350 (7-for-20) with two doubles and two home runs.
"The coaches have corrected a few things in my swing," he said. "I'm feeling really comfortable and hopefully that continues going forward. They brought me here for a reason. While I haven't had the results up to this point, I'm going to keep working hard to bring that production."
With the Tigers beating the Pirates earlier in the day, Seattle had to win to stay in a tie for the second Wild Card position. But with their three-game sweep, the Mariners have put a three-game cushion between themselves and the Blue Jays, the next-closest pursuer in the playoff chase.
The Mariners have been better on the road most of the year with a 31-23 record, but the successful homestand improved their record to 34-32 at Safeco Field. Of Seattle's 42 remaining games, 27 are on the road, beginning with a three-game series in Detroit starting Friday.
"It was a good homestand and our guys should be proud of it, but it's over now," said manager Lloyd McClendon. "We've got to get ready for the Tigers on Friday. We'll enjoy it for another 15-20 minutes and get our thoughts on them. But it was a great homestand, no question."