I have a Volvo Penta AQ131A engine and the guy who works on my boat suggest the carbs be rebuilt. I contacted a marina that stocks Volvo Penta parts for older engines and was told that one carb takes two kits and one carb takes four kits. In all I was told the kits would cost about $686. I thought that was pretty high, but really don't know. I looked up online and the part numbers are 856472 and 856471. Do I really need two of one of these kits and four of the other? If so, does anyone know if which PN I need two of and which PN I need four of?