The host nation are now second to Australia in Group A of the Rugby League World Cup and must defeat Fiji in their final game to progress into the knockout stages of the competition.
"Overall I'm pretty pleased," Sky Sports News quotes McNamara as saying. "We hit a real purple patch in the first half when we played with some great shape and executed some nice stuff.
"To nil any team, particularly at international level is a credit to the players.
"We weren't as fluent in the second half when the conditions were worse but we showed a bit of grit to keep them out and it bodes well."
Winless Ireland face Australia in the group's other concluding fixture.