I parked by the north shore of Lough Fee. There are a few small laybys along this stretch for parking. Better yet, there are three small wooden stiles to aid in crossing the fence at the roadside. Whether these are for the benefit of hillwalkers or not, I don´t know. I don´t imagine this hill gets much hillwalking traffic. This route takes the easternmost of the stiles. The others are within a few hundred metres.
Looking up from near the beginning to a false summit:
It´s just over a kilometre of walking and about 285 metres ascent to the top of Binn Mhor. The ground is rough and fairly complex, with the summit only becoming visible two-thirds of the way there. Good boots are needed due to the wet boggy ground on parts of the ascent. The high point has a biggish cairn with views down the Inagh Valley and west over the north Connemara coast and over Lough Muc to Binn Mhor´s higher neighbour, Benchoona. The summit area is somewhat sprawling and it is worth heading north a bit to get a more unobstructed view of Killary Harbour, with Mweelrea rising over it.
Summit cairn, looking towards the Inagh Valley:
Rather than heading straight back down, I crossed a couple of kilometres of mostly boggy ground to taken in some subsidiary bumps and descended to the side road that leads to Rosroe pier. The descent from pt. 203 (OSI 37) goes through some cliffs and outcrops and involved use of hands in a couple of spots. Care is needed but there are numerous other options for descent. Then there was 1.5 km of road-walking back to the car. This is a very scenic and normally very quiet stretch of road along Loughs Muc and Fee, with the steep, black north face of Benchoona looming above.
Looking back to the summit from further north-west:
Apart from the stile-assisted crossing at the beginning, this route does not cross any fences and there are few signs of human impact on the hillside. Binn Mhor is a Marilyn with a prominence of 268 m. There are more striking hills in the vicinity and Binn Mhor will not score particularly highly for aesthetics, but it still provides an enjoyable and peaceful walk for those who have already sampled the usual suspects in the area.
Benchoona and Lough Muc from the roadside: