Yaks are similar to a boat, they will get pushed by the current and you won't have a 4hp to help any. You can fit a TM to some models of yaks so that would give some propulsion other than manpower but depending on the current (# of generators going) it might be tuff with a TM and a full charge on the battery. With a TM on the yak, you have the extra weight when loading and unloading, would suggest a trailer then, and don't know if you want to go that route or not. Have some friends who have gheenoes with small OB's and a TM, one guy told me this past weekend that he runs his battery down on the Caney river over near Nashville when they are generating more than announced/predicted, and the river is too rocky in some places to use the OB.
GO BIG ORANGE !
I meant to behave, but there were just way too many other options available at the time.