Tateau18 - sent you a PM.
I noticed my fuel gauge had dipped below the 1/4 full marker, so put 20 gallons of non-ethanol gas in boat Friday night. When returning to boat slip from gas dock (5 minute ride), throttle surging was still present. Before l left marina, I cleaned the electrical ground on engine block with battery corrosion cleaner and a wire brush. It was getting late so I didn't take boat for a drive after cleaning corrosion off engine ground.
Today I took boat out on lake and the engine purred with no hint of surging! I throttled up 8-10 times from 0-35 mph in the few minutes I had to be out on the water and the 8.1 never surged. I'm returning to the lake tonight to confirm the surging has been resolved, but I'm cautiously optimistic it will be.
Any ideas what was causing the throttle surge and what I did to fix it? In 16 months owning my boat, I have never let the fuel tank get this low (always refuel to full tank when gauge is half full).