I like to share the solution to the drive train vibration. In spring I send the VariProfile propellor to the manufacturer in Germany for restoration. However its was out of the specs to be restored. For a quite a sum of Euros I now have 3-blade (in stead a 2-blade) VariProfile featering propellor and vibration is almost unnoticeable. The unbalance in the worn old propellor probably caused the stern tube to come loose. All is fixed and I’m sailing (and motoring) happily.
No wishes on the drive train? Yes, of course. I think the Yanmar 2GM20F is a fair engine, but a bit underpowered for the 335 .. in combination with this feathering propeller. I can reach 5-5.5 kts when pushing the engine.