The Irish were trailing 3-2 after the foursomes, despite in-form duo Dermot McElroy and Kevin Phelan claiming the opening encounter 3&2 over heavyweight Scottish pair Graeme Robertson and Jack MacDonald.
Ireland also took game two but it was a close tussle, with never more than one hole separating the pairs before Gavin Moynihan and Chris Selfridge won on the final green against James Ross and Ewan Scott.
However, the final three matches of the morning session belonged to Scotland as they ensured the Irish would head into the afternoon session trailing.
Moynihan notched up the first point of the singles but Phelan, who was ahead for large chunks of the match, failed to close out against Grant Forrest, with the Scot fighting back to take the tie 2&1.
Three-and-a-half points from the next four matches out on course, however, set Ireland up for a sensational win, McElroy edging a titanic tussle with Jack MacDonald on the final green, before Casey and Dunne each recorded comfortable wins.
Alexander Culverwell’s clinical victory over Cormac Sharvin put Scotland back in with a shout, but a Houdini act from Jack Hulme, who was behind practically the whole round to Scott Crichton, saw the Naas player come back to win on the final hole to settle the clash.
McNamara added some polish to the scoreline with a 4&3 win in the last match.
In the day’s other match, England trounced Wales.
Today, Ireland will face a winless Wales and hope Scotland are able to do their Celtic cousins a favour and beat England.
* Robin Dawson produced a stunning comeback to edge past friend and compatriot Gareth Lappin and move into the third round of the Boys’ Amateur Championship over the Royal Liverpool course at Hoylake.
The 17-year-old Irish Boys’ champion from Faithlegg was down almost the entire way but then fired a string of birdies on Hoylake’s tough finishing holes to record a 19th green success.
Two down on the 17th tee, Dawson hit a superb 3-iron to within eight feet of the pin and knocked in the putt for a winning birdie and got a birdie on the last to tie things up. He had also birdied both 14 and 16 so collected four in five holes, two of which were halved.
Then at the 19th, 18-year-old Lappin went out of bounds with his second shot and that was the end — Dawson was through to the last 32.
Dawson now plays Scotland’s Adam Fisher in the third round this morning.
Dubliner Paul McBride was in fine form as he put Portugal’s Joao Girao to the sword, getting to three under par in winning 5&4.
Earlier, Jake Whelan went down on the home green to Welsh teenager Otto Mand.
* Pádraig Harrington could only manage a three-over-par 73 in the first round at the Wyndham Championship in North Carolina.
American Chris Stroud set the early pace with a six-under-par 64.