Sorry if this upsets anyone who thinks their Yanmar is a "purpose built marine engine" but Yanmars are converted tractor engines, just like Kubotas. See yanmartractor.com.
Also, John Deere engines and tractors are rebadged Yanmars which is why you don't see Yanmar tractors in countries where John Deere are sold.
There's really no difference between a Beta or Nanni based on the Kubota tractor engine or a Yanmar based on a Yanmar/John Deere tractor engine, except the silly price of spare parts. For the Kubota-based engines you can readily buy the parts at tractor prices, Yanmar not so ea