Go to NADA boat prices and you will get some idea of what the rig is worth,I couldn't find Blue fin but did look at aluma craft of the same year,the boat is worth $700 to $800 the trailer is worth about $300. The motors not worth much as you've found out already.I just picked up a 89 Starcraft 18' with a 70 Hp merc and trailer all in great shape,The guy was asking $4,000 the book had it around $1,600. That's what paid
I did like you said. 1988 Blue Fin w/ a 50hp books at $1,195.00.