How difficult is it to replace the gasket between the pump and the engine block? Where can I buy the proper gasket? I can see where I have some saltwater leakage. Is it necessary to rebuild the entire pump? It is not that old but I did have some excessive engine heat for a while. Temperature got up to 200 degrees, normally runs at 140. Had an engine exhaust leak which caused the engine room to get hot, hot enough for my Fireboy to self-discharge. Got the exhaust leak repaired and she ran beautifully another 800nm (75% motoring).