Running Rough - Any Ideas?

Boat is running rough. Idles fair, runs high speed ok. Mid range is rough. Had this before in another boat, it was the plugs. When idling in the drive driveway, I pulled each plug wire. Made no difference on three plugs so I replaced all plugs. Still the same. Tested plug wires and found no continuity on some. Replaced all wires. Still sounds a little rough (haven't had back in water, so not a great test yet) What is next? Timing? Which would be bad, since I don't know how to do that or have a light. I have heard of people adjusting timing by sound...is that doable? Or might it be something else?

leave the power valve alone unless it is backfiring.

Set the timing correctly then start adjusting the carb and looking for vaccum leaks.

sounds like a vaccum leak somewhere, or a fuel delivery issue since it's an off idle surge. Which hole is the accel pump in? there' an arm on top of the carb and two dog ears cast into the top of the carb with a roll bin through it that the arm for the accel pump pivots and on that arm should be two holes, so is the hole that isn't used closets to the pump or in between the pump and cast ears or on the other side of the ears toward to outside of the carb?

Did everything I could and still ran crappy if not worse. Gave in and took it to local shop. He checked timing, ok. Changed fuel filter. Took off carb and tried to blow it out to clean it. He said it was pretty crappy inside. Still ran crappy for him.

Decision time. Do I have him rebuild it ($60 for kit, about $300 total, or do I get a new carb from SKIDIM ($500). The mechanic says he will rebuild it but he doesn't like Holleys and says there are a million nooks and crannies where stuff get clogged, and he makes no guarantees on his success. The boat is 16 years old (not my Tique, my other one) about 600 hours, and this guy rebuilt the carb about 5 years ago.

OK guys - what do you think? rebuild or new.

My holley kept running like crap 2 years ago (after 2 rebuilds) and I took it to Carolina Carburetor Specialist Inc. They tested it by putting it on a flow bench and running mineral spirits through it. They said the metering block was defective. So I traded my carb in and got another one, I think it was $175. 1020 Princess Street Wilmington, NC 28401 910-762-4695. These people know carbs, it's all they do.

ethanol has been in gas for years and is nothing to worry about, now if you used the e85 stuff then that's different and it won't run right with out major changes to the carb.