[staylor]

...since you're only firing 2 cylinders per revolution. I have a similar bit of prop rattle/vibration at low speed idle in gear with my 150 Merc 4S and a Tempest prop. I discovered that switching to a Trophy Plus 4 blade- which has a small hub and thus vents around and through the hub eliminated the vibration completely. I suspect that the exhaust flow over the small hub at low speeds is providing a dampening effect on the engine to lower the felt vibration. As Mr Ducks and Oilguy have posted, the latest FloTorque IV hubs help a bit, but they don't eliminate the vibration altogether.

The only downside to the Trophy Plus props is that they don't hold plane at low speeds as well as a full hub prop. In my case I have a fairly light boat so this has not been an issue. If you're interested, just borrow a Trophy Plus in any pitch for a quick test at low speeds to see if that helps on the Verado.
Doug