I keep having a lot of cooling problems with my 66 ocean ss with cat 3412´s. Unfortunately, the area I cruise has a lot of trash floating around. I´ve gone through about 8 impellers in the last year and a half, and I always find plastic bags clogging my intakes. Many of the other boats of the same size as mine keep having the same problem. Someone told me about converting my cooling system to a closed one. I would think that this is not an easy task, and have never seen it done on a pleasure boat. I have done it on my work boats, but those are slow speed, metallic hull boats. Anyone have any experience on this or have ever seen it done?