Just sent my broken HDS 9 Gen 3 unit to Lowrance and upgraded to HDS 9 Live unit. Same screen size and fortunately all the same connections and transducer so I don't have to re-wire anything. BUT, the new unit is slightly wider than the old unit and now it won't fit in the face plate. About 1/2 inch off due to the side knob. What do I do?? Never had an in-dash unit so working with a face plate is new to me.

That looks like starboard or some similar plastic material. Correct? Got any hands-on tool skills? Got a trim router with a straight bit? That unit should have come with a template in the paperwork with it. Take a look. It should be used to center the unit's cut-out pattern over the hole you already have. With that much space, the mounting holes will be moved out to new locations for all 4 corners. A hole too small is a lot easier to alter than one too big! With the proper tool and knowhow, the fix for that is a 10 minute task.

Yes, don't know what starboard is but it's a hard plastic material. Has obviously been cut to fit prior unit. Unfortunately do not have a trim router but can maybe borrow one. May be a dumb question but would a sander work for expanding the sides on that pastic? I'll look for the paper template to use for new mounting holes.

You can use a sander but it will take some time sanding starboard. Also, you will probably go through a lot of paper as it will just melt to the paper.

Go to harbor freight buy a cheap jigsaw and proper blade. Should be less than $40 in materials and you will have a new tool.

Thank you! Jigsaw should work. Will pass on the sander idea.