The wheel isn't for steering, there is only one and I think steering pullers usually are mounted sideways...I also don't think it is or an anchor system because it is too small.
Could it be a guide for trolling behind the boat? Rest your line on it or something?
The idea that the brackets could have been for a set of wheels kind of makes sense...I think I have seen a boat equipped with them before but did not see how they were attached so I don't know...