Stehr? Never heard of them
Steyr make real good top notch guns.
They also used to make diesel engines and cars and motorbikes but that is ancient history.
Their modern diesel engines are called "Chainsaw" engines because of high revs and light construction. Also the concept of no head gasket may seem great to the novice, but good luck if you need to do any work on the head.
Time will tell, they do look nice.
i would have gone for a Yanmar. and a V drive and dump the stern drive. Sure, some mucking around with the hull required.