Summerhill, the 2015 beaten finalists, made it back-to-back wins as they got the better of Marist College and stayed top of Pool 2 in the competition.
The Sligo school defeated the Bish 11-3 in the opening round, as they backed that up with another hard-fought 10-9 victory at Marist.
Summerhill have never won the Senior Cup but they only lost by a point when Garbally beat them in the decider two years ago, and they will hope to continue their great form against local rivals Sligo Grammar next time out.
In Pool 1, reigning champions Colaiste Iognaid are joined at the top by surprise packages CBS Roscommon.
Roscommon won the Junior Cup in 2015 and look to have a strong side in the senior equivalent this year.
In the Junior Cup, St Muiredach's of Ballina have never won the title but they produced a brilliant 60-10 victory over St Gerald's of Castlebar at Ballina RFC.
The Ballina outfit are top of Pool 1 with ten points after two games and they will be difficult to stop after scoring 106 points in their first two matches.
In Pool 2, Sligo Grammar are top of the pile on nine points after three games, despite losing 25-12 at home to CBS Roscommon at Sligo RFC.
The other game saw Garbally come out comfortable victors on a 59-3 scoreline over the Bish at Ballinasloe RFC.