Rusty barge..why run anything in the water when you can keep it safe in the hull.
How would the USCG define this..Inboard or outboard..or illegal.
Another great idea,Tom!
I love your drive system, but having to cut up and modify the hull of an old GRP boat hull which will have soaked up decades of moisture is beyond my laminating skill set; I'm more of a amateur steel fabricator!
my project idea was based on buying an old twin screw 12mtr or less s/d motorboat with twin 250hp diesels from the last century, the 90's

; there is zero demand for gass guzzlers like these, you can nearly take them away free!
So......
Using the Japanese 'UV joint in the prop shaft idea ' ....
.....and Tom's idea of an old outboard hung on the transom to provide the 'up and down' tilt mechanism .......
......to locate and lift the extended prop shafts that stick out past the end of the transom........
.....with the prop shaft located into the old OB bottom unit without the bevel gears, using the trust bearing already in the bottom unit (machine a suitable through hole like in Tom's photo)'......
A rudder could be bolted to the OB leg.
A neat ready made solution, easier than fabricating a lifting swim platform!