Hi,
My guess would be that the
price difference comes from the fact that the IP 31 is a mid/late 80's model, while the IP 32 is an early/mid 90's model, and you're primarily witnessing the $$ depreciation curve.
Not knowing anything specific about these models, but drawing on
boating experience in general, I think there is likely to be little difference between the two. After 15/20 years,
ownership maintenence is the primary deciding factor on condition, not age.