New (to me) '98 90hp Honda owner?

[ahicks]

I have a question about vibration coming from this engine. It seems to be running perfectly, but it's like the engine is bolted solid to the transom - with no vibration isolation. It's like the motor mounts have hardened to where they are not effective? Never heard of it, but wondering if that might be something typical? It's OK at some rpm's/speeds, but setting up harmonics in the entire boat at others. I have another pontoon with an '07 Honda 50 that's silky smooth through the entire rpm range, nothing like this at all, so the vibration coming from this 90 has taken me completely by surprise.

Thanks for any opinions/input/ideas