Sometime boxes, for lack of a better name, like you have are used to contain flotation foam. Maybe not because there is an access hole for battery cable, fuel hose, etc. in the left one.
If the front or better yet sides can be removed, the nuts will be staring you in the face.
GA Boater, There are still bolts going through the transom that I have no access to because the splashwell is in the way. It seems ridiculous to have to remove the entire splashwell to change the transom.
yes the splashwell has to come out. not all of mirrocraft boats got a splashwell. the splashwell was added after the transom was put in. the same basic hull went as either a pure fishing boat or a fish-n-ski
remove the splashwell (a bunch of rivets) and continue to remove the bolts thru the knee brace