Treasurer is a position that generally requires some experience in some ways. Does he have any experience in an organising role?
Also - find, or even create, a grievance. So, for example:
We don't have enough Pool Tables in the Common Room! As your treasurer, Joe Bloggs will ensure that we get funding for more pool tables.
Obviously, don't pick something out of thin air. Find something that actually is a grievance/problem, as well as being something people actually care about.