I don't know what is causing the vibration, but I have looked at all the obvious and some not so obvious causes. It does not vibrate running at the same rpm in neutral, even loaded a little (I can load it to about 15 hp with the alternator). The prop has been checked for balance. Everything is new. I haven't checked the shaft with a DTI (I intend to), but it is not visibly bent. The drive leg may have been contacting the hull fairing strips, we opened that up and I think it improved some, but still there, rechecked it is no longer hitting. There are no obvious resonances, boat starts to vibrate at about 1500 and continues to 3000. It isn't severe vibration, just annoying - especially so since the saildrive is supposed to isolate vibration.