The section from Lolo Pass to Marmot (Sleepy Hollow Bridge) is boulder filled and changes year to year. It is mostly class II with some class III areas at regular flows. The run becomes fun class III-IV at high flows, but wood is sometimes present . At very high water (rocks heard rolling along the bottom) the confluence with the Salmon gets turbulent and the rest of the run is a fun flush down the middle with large waves and some holes that can sneak up on you.
The most distinct rapid are the class IV Alder Creek Rapids, near an A-framed house on the left. Scout this rapid along the bedrock on the right. From here to the old Marmot Dam sight is class II-III with a sneaky hole at the end of a long straight away a mile or so below Alder Creek.