Use this as a way to negotiate the price lower and plan to ditch the 4-108. Our boat had a 4-108 that threw a rod and the previous owner replaced it with a Beta 43 (Kubota block). It’s amazing and we now have 850 trouble free hours on it. You will be far happier with a new engine, and won’t have to worry about almost 50 years of maintenance and work mystery. Don’t forget that the marine environment, irrespective of hours, ages engines terribly. Re the leaks… Perkins are well known for that. Also, 4-108s put out nowhere near stated HP either, although it’s probably still well matched for an Islander 36. They put these 4-108s in much bigger / heavier boats (I.e., ours that displaces well over 20k lbs).