1988 Johnson 70HP - stalling when first put in gear - how to drain and clean carbs

I have a 1988 Johnson 70hp outboard that I just bought used. The guy I purchased it from has receipts from a boat mechanic showing that it was rebuilt back in December 2012. Since then the seller told me he hasn't finished breaking the rebuild and has put only 4 hrs on the engine, meaning its been sitting at least off and on for 7 months. I ran it about 4 times putting another 6 hrs on it, following the manual protocol for breaking in a motor which required doubling the oil. The boat runs great once on the move but the motor constantly stalls as soon as it is put in gear at low rpms. I make sure that it is fully warmed up (idling for at least 5-10min) and this doesn't help. I've also tried turning up the idle and this hasn't helped any. The plugs look pretty good when I've checked them too. I'm thinking the carbs need to be cleaned but I'm pretty novice to boat engines. Has anyone had this problem and knows what the issue is likely to be. I'm wondering if it is just the double oiling is causing combustion difficulties, but this begs the question, how do people properly break in a 2-stroke outboard without putting a ton of wear and tear on the starter etc? Spoke to a mechanic who said to take the carb plugs out, drain the carbs and spray carb cleaner in the plug hole then pump fresh gas through before trying to dismantle the entire carb and clean it that way. Has anyone done this or recommend against it? If I take apart the carbs is there a serious threat of messing up the fuel/air ratios etc.? Thanks for all the help.

Re: 1988 Johnson 70HP - stalling when first put in gear - how to drain and clean carb

You can try the carb trick first and see what happens. If not the carbs should be rebuilt and if you get them good and clean you shouldn't screw up any ratios.