I second what Cat_Driver has mentioned above. From past experience my 2 cents worth.
I mean no disrespect but have you considered hiring an experienced contractor who specializes in this sort of thing? Without knowing what your repair budget is, it would be difficult to try to estimate how best to proceed. You are working with a top heavy old balloon framed structure with no connection between the two outer walls at the water line. You are also dealing with a dynamic system in partial collapse. The first thing that should be done is stabilize the boathouse framing as it is with cross bracing horizontally and vertically so it will not collapse any further. The advice of all the others above is good and well intentioned but without being able to be sure of what has already been done and to what extent it has actually mitigated the collapsing cribs that advice is based on assumptions which may not be supportable.
If your cribbing has settled as much as you described, you are wasting your time trying to manipulate the framing above the water line until you permanently stabilize and reinforce the foundation on which it is sitting. That should be your first objective. It would be a shame to have the boathouse collapse not to mention someone getting hurt because the cribbing gave way after you had gotten the structure partway repaired.
The cribbing is fine and stable, and we are using a de-icer in the winter to prevent ice damage, which is probably what caused the problem in the first place. So there is no further work to be done there. We just need to put the decking back on either side after we get the walls situated horizontally.
And I don’t think the problem is due to age-old warping. In fact, as you can see from one of the pictures, I USED to have them in the right place - you can see the clean spot where the bottom of the wall used to be, about a foot to the left of where it is now. It just doesn’t want to go back there again now.
This coming weekend I will be putting up some scaffolding inside to have a better look at the roof boards, because the plan is to completely reshingle the roof once I get everything in the exact position that I want it.
And thanks for the good suggestions out the plumbob. Actually, I can eyeball it pretty close, and the lien is quite obvious. In the end I can put up with some lean as long as it doesn’t look obvious.
Here are some more photos.
That last photo was taken in the fall, when I rebuilt the floor outside the boat house with new concrete. It is now a good boat ramp. And you can also get an idea of the lien on the right hand side, where I have bolted a couple of 6 x 6’s.
And thanks for the nice compliments as well, guys. I agree that this boat house is magnificent, and a landmark on the lake!