I have this engine on Bristol (it is a bit small for 36k displacement) and it has worked very well. Some parts are ridiculously expensive - I had to replace the double pulley for the freshwater pump
and it was more than $500.
The block is a Mazda tractor engine that is widely used in Asia and Europe but I could not find a dealer in North America for these tractors.
I know a really good mechanic in Noank who could survey your engine. His name is John (forget his last name and it is not the John who runs the yard) and he works at Spicer's marina. Knows his stuff and very friendly - tell him Bruce from Ainia says hello.