What is the model number of your engine. Mercruise did not use a 302 Chevy. There were 302 Fords, and 305 Chevys. Is there a Merc SN? There should be a tag just above and aft of the starter, on the block of the engine.
Sorry to change the subject but I have to ask. What is the big 3" diameter piping going to the stern for?
I saw that too and wondered if that was some sort of "aftermarket" fuel hose.