The only reason the rear seat bottom had to be replaced was some unknown solvent drop got on the seat and hardened a spot which cracked the vinyl. Do not let seats bake in sun or get rain soaked. Do not let guests step in seats. Use only oil-free sun block and tan lotions. Remove seats, clean, and store at end of season.
Purpose is to allow flushing of coolant system with fresh water esp.
If your engine ever overheats check this valve. Debris has been known to keep the valve from opening, causing overheating. The guts of this device can be removed or entire device deleted if you don't use the transom flush connection. While reading past messages I noticed several inquiries for Donzi sales portfolios. This Portfolio was used for a couple of model years, so is undated.