I've only had my SIB for a few weeks, but notice a bouncing at about 30kph+. It is not wave based and even happens on flat lakes. It seems to be when I have one passenger up front, but I have not tested this in detail.
Any ideas if this is a form of resonance? If so, can I do anything to supress it? It is no biggie, but makes the passenger uncomfortable.
It's a OMC Express 305 with a Mariner 15M (short shaft) on the back.
Loving the new hobby though