I found the police to be very good in finding stolen property, they just don't like giving it back...
About five years ago I bought a brand new generator to use with my (then) newly acquired caravan...gennie was delivered next day, so I put it in the garage ready to try out at the weekend. Weekend arrived, I went to the garage (door still padlocked and secured), opened up and found...no gennie. Called the police, and out they duly came, did all the taking of statements, fingerprinting everywhere, and off they went.
Middle of the following week, I received a phone call from them asking if I would pop into the police station and identify a gennie...I took all the paperwork, invoices, etc...everything matched, it was my gennie, still wrapped and boxed. I was told it was needed for evidence, and they would call me and let me know when I could have it back.
After a year I gave up...we'd sold the caravan anyway, and I'd moved out of the marital home. I never did get my gennie back, despite many a phone call...
Hope you have better luck with your outboard, Ben...
Rich