If they are just a floury variety they're great for roasting, parboil them for 5 minutes, then smother still hot in duck fat or olive oil , then in the oven (yum).
I never remember which I planted where, its' trial and error with the cooking method every year...We had very watery ones last year, nice for mash. Must have been all that rain...
Did you peel them? We never peel our own before cooking, keeps all the goodness in and they do stay together better. cooked peel you can feed your birds if you have any, they love them.
Other than that, as Russ said, try boiling them for a shorter time. We stick a clean knife into them after 10 minutes, if it slides out without pushing, they are done. Depends on the size as well.