Having Mercury problems

Have a 05 50hp 2 stroke that I can't keep out of the shop..I have all 3 carbs done and replaced every fuel line on the boat. New plugs, filter, and primer bulb and line. Today we took the boat out and it ran fine until we get ready to leave. We idled out of a cove and I began to throttle up took off like normal until 4k rpms boat shut down completely. Got it fired back up and would not go over 2k rpms so we limped back to the ramp and it didn't even have enough power to get back on the trailer. Got it home and started looking it over, cranked it right up on the muffs and I'm getting some backfire and high idle 1500 rpms. Checked compression for some peace of mind got 120 across all cylinders. It didn't have a high idle on the water but would gradually rev up over 2k on the muffs just not on the water. Any ideas on what to check..it's to the point I'm ready to scrap this thing find a new motor. When it's running it runs great..but I've had out probably 4-5 times and has gone back to shop 3 times.

Sure sounds electrical. Has the stator, switch box and timer base all been checked? That’s where i’d be looking.

Don't know where you are but if in the Longview area, contact TOWN & COUNTRY MARINE, east of Longview on Hwy 80. Joe knows his stuff on Mercurys cause that is all he works on.