A last-gasp winner from Ryan Boulding gave United a 1-0 win over Aberdeen on Saturday that saw them pip both the Dons and Kilmarnock to sixth, with Killie suffering defeat against Dundee.
And McNamara is keen to close ground on third-placed Inverness over the remaining five matches of the season.
"Inverness are seven points ahead of us and that's the target now," said McNamara. "Today was about winning and doing our jobs properly and we did that.
"It was a great feeling to score when we did.
"We were on the end of a late goal from St Johnstone the other night and we were a bit deflated after it. This goal more than makes up for it.
"I think it was deserved, especially in the second half. I was just delighted for everybody connected with the club.
"We've had a couple of disappointments over the last couple of weeks and today makes up for it."
Two ex-Kilmarnock players sealed their fate in the end, with Gary Harkins grabbing the winner for Dundee and Boulding netting for United.
McNamara added: "I'm delighted for Rory. Pipping his old team, after being released by Kilmarnock, I'm sure will be a good feeling for him."