I have a 1981 Pathfinder w/ 7000 hours. It's had a head job and a new exhaust/heat exchanger a few years ago but it's doing OK. This spring it hadn't been started for 18 months and it only took two seconds for it to kick off with no smoke or any other problems.
I did winterize it and drain the coolant for the duration. They do have a lot of alum. innerds so the proper coolant is a must. They are a light weight motor but 10K should be fine, mines 15K. The 50 hp are hard to find parts so I'd go a different motor.
The truck/cars had a different cam shaft, more for high speed (up to 4K) but the marinized has a torque cam. If this were the 80's or even the 90's I'd buy another one but not now.
The new (small) Pathfinders are now 65 hp and a bit larger. I retrofitted a larger raw water pump because parts were not available for the old one. Plus, I'll be adding a "T" w/ a stainer on the inlet side to go down to the bilge for a backup/emergency pump.
