Unless it came from Mercury. 575's and I believe others came with flats

Yes. Mist the wires with a spray bottle of water, turn off the lights, and look for the light show. A non firing plug due to shorted plug wires, will def cause a rich exhaust, and make a ticking noise.

Hard to speculate these kinds of issues over the computer. A mechanics stethoscope or long screw driver to your ear can help isolate where the noise is coming from.

That still baffles me. Why mercury would put roller lifters in the HP500's, 500EFI's, but not the 575sci? Weird.

are gen 5's flat tappet?

yes.

How else do you get rid of the pile of camshaft and lifters in the back room?

What an improvement it was changing to an agressive full roller from the very conservative flat tappet. I really should put my pulleys back to stock and see what I got out of just the cam change

Becareful with you long screwdriver in your ear next to that arcing wire haha