Slitherine

Is it possible to set a port so that it can supply your ships, but not repair them? (I'd like to make some "small" ports that don't have the facilities to repair ships.)

AFAIK, what you want to do is not possible, though I have not tried it myself. The info that defines those kind of parameters is found in the "terrain.pzdat" file, located in the "Data" folder. I believe the trait "navalsup" allows for both naval resupply and naval replacements; I don't think you can separate the two. But this is where you would start.