I bought the boat last August with supposedly 460 hours which is also what the hour meter said. In the last few weeks I've done the impeller, fuel filter (filter was collapsed) and installed a pertronix ignition conversion along with cap, rotor and plugs. I first noticed the sound yesterday after finishing the ignition but I can't guarantee it wasn't there last season. Oil psi per the gauge is 30ish but the needle bounces some. The previous owner told me he always ran high octone and between that info and the new ignition I'm really worried about detonation. I have not checked or adjusted the timing. Boat is hard to start but I don't think the choke is closing and pretty sure the carb should be ran through. I had to turn the high idle up to get it to idle smoothly.
