1976, to keep or not to keep?

[Nightfire]

I have a 1976 Chaparral 165 that is in good shape for the year, but the motor isn't very reliable it has small problems here and there every once in awhile. The motor is a 198? 70hp Merc, do you think I should spend about 6-7 grand on a new 4 stroke motor, or sell the boat and buy a new one for about 20,000? Here are pics of the boat and motor- http://www.imagestation.com/album/pictures.html?id=2101516616
If the general opinion is to sell, is anybody interested for say $800.00? I'm in Jacksonville, NC.
Thanks!