The million dollar question.
I'll be frank. Project boats appeal to buyers with the necessary skills and finance to complete them. We're already looking at a niche group of people.
You've had it for 2 years and have had it re-tubed, so at the very least try and recover what you paid for the retube, and the bare hull (not including remedial work). Buyers will ultimately question why you're walking away from the project part-way through.
The engine is interesting, but it's old school technology now, regardless of whether it's still new. At 2002, it's now 14 years old, and a real gas guzzler so be realistic as to what you'll accept.
It comes with a trailer which is new. Trailers don't lose money, so you can basically recover what you paid for it, give or take a few hundred pounds.