Oil temperature problem

This is a certified engine used in a certified aircraft.  Tecnam should have an answer for this.  The normal fix would be to block off some airflow to the oil cooler however you must be sure that is does not then lead to overheat in the full range of conditions.  In experimental aircraft this is often done by a temporary block to cover a portion of the cooler.  i might start with just using a tape over perhaps 10% of the cooling fins to test.  One must use caution and not block too much airflow as this same air might be cooling other portions of the engine bay. 

Cheers