Welcome to Yacht Forums. Cummins manuals are everywhere. Boat/hull manuals from a long closed shop is sadly going to be a challenge. Hopefully another Luhrs owner has something to help. Took over 10 years till I found a new best friend with a Bertram manual copy. In that time, I had already compiled notes filling a few large binders and many gig of photos. Found the long awaited factory manual worthless and full of errors. Luhrs are plastic boats. Just like many, many other plastic boats with the same parts in use. If something is broke, jump in and fix it. Plenty of data on many boat options. Where and how to access it is the challenges that a factory manual probably would not help on anyway. Document it well and ad another chapter to your new manual. Your ships value can improve with data and service history. Good luck.