Hi guys last time I brought a water pump repair kit it included a gasket to sit under the steel plate, I'm replacing the impeller but to get a new gasket it looks like I need to buy a whole repair kit instead of just the impeller. When I look at the schematic it doesn't show the gasket, is the gasket necessary or does it just come as an extra in the repair kit? It's a 1980 50hp model number J50ECSR