- show quoted text -
I just spent some time Googling up boat manufacturers and finally
remembered the manufacturer of my first boat. It was a "Regal".
It was a 20 foot I/O and definitely had the 4 cyl "Iron Duke" engine
although Mercruiser called it something else. Looked similar to this
except it had a cuddy cabin instead of an open bow.

https://i.ytimg.com/vi/GMOvwNkkOWo/maxresdefault.jpg
....

That iron duke is otherwise known as a 3.0L which was ranged in 120-145 hp. Depending on carburation, cam and compression. They smoke a but but are tough little buggers...