Small Engines (Lawn Mowers, etc.): B&S 5hp 4 cycle Outboard sputters past 1/2 throttle., briggs and stratton, jon boat

Question
Hello,
This service of y'alls is awesome.  My kids saved up their money and bought a jon boat that came with a 2002 Briggs and Stratton 5hp OHV 4 cycle outboard motor...basically a lawnmower with a prop.  The thing seems to run quite nicely at idle and low throttle.  Once we try to put the throttle past 1/3, and especially past 1/2 throttle, the thing sputters, pops, and has very poor power and kind of surges with what power it does have.  If we engage the throttle a bit at higher throttle it smooths it out a bit but we don't want to do that at all.  We took out the spark plug and replaced it with a new one that is gapped properly.  My uneducated guess is the carb needs cleaning but I'm a motor moron who has never cleaned a carburetor.  What is your professional take on this problem and do you have any suggestions on visual and written aids so I don't completely ruin my kids engine.  Thanks a ton.  Blessings to you all for a great service.

Answer
It sounds as if the transitional circuits in the carb are some what plugged. Maybe with varnish from the unit sitting around a little while. This is a very common issue. If you have never rebuilt one of these carbs, don't worry, theres not much to it. The biggest mistake on most peoples parts is the cleaning process. If it is so that the carb suffers from varnish build up, it will need to be acid boiled and then run through an ultra sonic cleaner to properly remove the varnish that is causing  your problem. It may pay off for you to take the carb to local Briggs dealer to have them perform the cleaning process for you.