After I replaced me blown hose, I was heading home from my buddys dock ( 5 min). once I got home had it idle while I gathered my ropes and fenders, I herd a knocking like sound. It wasn't constant or timed. I lifted my hatch and it became more evident. If I rev it up just off idle its gone. If I switch on my silent choice its gone completely. It sounds like my thew shaft, but that wouldn't change if the exhaust was on or off. The engine got hot but did not exceed 240. I'm changing plugs this afternoon. Anything else I could check if the plugs don't help?