I am fairly new to Sketchup and this community. I briefly used SketchUp a few years back and started again recently because I purchased a 3D Printer.
I downloaded a yacht model from 3dwarehouse, modified it and converted to .stl but does translate well in the slicer. I believe it is related to the walls being too thin, windows, gaps, etc. I’ve tried everything I can think of to no avail. Not sure how to fix the model.
The walls aren’t just thin, they have zero thickness. You could make a sort of bathtub shape to fill in the hull but there’s also a lot of areas that are going to need special attention. Examples:
In order to be suitable for 3D printing the model must be a solid group or component. That means that every edge in the object must be shared by exactly two faces. No fewer and no more. So no stray edges, no holes in surfaces, and no internal faces. In addition, all faces must be properly oriented so their blue back faces are oriented toward where the print media will be. In order to make sure the face orientation is all correct you need to use a style that doesn’t display materials.
Your profile says you are using SketchUp Free (web). While you can fix up this model, it’s not going to be a simple task. Since the hull is symmetrical you might split it along the keel line and work on just half of it. Once you have that all correct, you can copy the geometry and flip it to make the other side.