Ouellette ME is not actually an incorporated town or village. It does appear in the DeLorme Road Atlas at the intersection between Route 161 and Flat Mountain Road (leading north towards Saint Agatha ME), but there is no town there.
Ouellette was never incorporated or organized for election or tax purposes. It appears to have been a locally-used name for the area (really just a few farmsteads), but it has and never has had any civil or legal status. I suspect that it appears in the DeLorme atlas as a way of making the map unique for copyright purposes (as do a number of other rather insubstantial communities and a handful of non-existant bridges).
The intersection marked "Ouellette" in the atlas is right in the center of T17 R5 WELS ("Township 17, Range 5 West of the Easterly Line of the State"). This is one of Maine's many "unorganized townships." It has no township office and it maintains no records. Civil records are apt to be at Fort Kent or Saint Agatha; church records would be at Holy Family parish in Daigle ME (now decommissioned, records at Saint Louis parish in Fort Kent ME) or at Saint Joseph's parish in Sinclair ME.
Acadian Archives/Archives acadiennes
University of Maine at Fort Kent