Has anyone ever used, or heard of the 1.6 or the 1.9 being used in a Marine application? Like as a inboard?
Yes! I've seen sailboats advertised with VW 1.6 NA diesel inboards.
If I remeber correctly, there was a company in Quebec that made the engine mounts & adapters for marine applications.
Google
"vw diesel" + inboard
You'll get a few hits.
I think they were called Pathfiner engines