Poehling drew Montreal to within one twice. He made it 3-2 at 8:51, the third goal at 4-on-4 in 48 seconds.
After Ovechkin's goal put Washington ahead 4-2, Poehling cut the lead again to 4-3 at 2:22 of the third period.
Garnet Hathaway made it 5-3 at 3:08, Orlov increased the lead to 6-3 at 4:30, and Justin Schultz put the Capitals up 7-3 with a power-play goal at 9:50.
Nick Suzuki scored his 20th goal at 14:53 to draw Montreal within 7-4. T.J. Oshie scored Washington's second power-play goal at 16:35 for the 8-4 final.
"We play fast and it's a fun system to play but you've got to be honest about it," Poehling said. "You've got to play hard defensively, and when we do that and you see it out there and we're on top of guys, it's hard to play against and we end up with the puck a lot more. I mean, even against the Islanders you saw that a bunch and tonight in spurts too.
"So I think that's just the things you have to do, and if you can do that right now and just kind of make that part of your game, I think the game comes a lot easier."
NOTES: Ovechkin is one from tying Teemu Selanne (48 in 2006-07 at age 36) for the most goals in an NHL season by a player age 36 or older. It was the first time Washington scored seven goals or more against Montreal in 181 games between the teams including the Stanley Cup Playoffs. … Evgeny Kuznetsov set up Oshie's goal to reach 50 assists for the fourth time, second in Capitals istory behind only Nicklas Backstrom, who has nine 50-assist seasons. … Mantha's goals were the fastest two goals by a Capitals player since Oct. 4, 2018, when Oshie scored twice in 21 seconds in a 7-6 loss in overtime at the Pittsburgh Penguins. … It was Orlov's first four-point game, and the first by a visiting team's defenseman in Montreal since Pittsburgh's Kris Letang had four assists against the Canadiens on March 2, 2013.