Concerning the Honda: Honda's (and the 4-stroke Tohatsu's for that matter) have very small pilot jets which are solely responsible for the fuel part of the fuel mixture at Idle. They also are still "in the circuit" when you crack the throttle open all the way to WFO.
Because they are so small, they get clogged easy. REAL easy. So you are correct in one assumption: use clean fuel, if you have a plastic tank, peer into the tank and make sure there are no "floaties" or trash in there.
Symptoms: Dies at idle, especially after you push the choke in. Using the choke to have it run is part of the symptom, meaning having to keep the choke on to some degree all the time. I have a older Honda "blue leg) 7.5hp and as soon as I had to keep the choke on when it was running, I took the carb off and blew out the jet(s). When I put it back together, everything ran fine.
Another symptom is heating up. Because the pilot jet lends fuel to the fuel mixture even off of idle, not having it in the circuit (helping provide fuel to the air) when at other positions can make the mixture lean. Lean means heat. My "Spidey-Sense" says this is probably not the case with you, but I am just Thevan-izing.
Taking it to a dealer is hit and miss. Some dealers are respectable and have competent staff that do the work, some don't. But I don't trust them to mess with my outboards. Thus, I may not do everything "according to Hoyle" but I have learned about my motors, sometimes the hard way. It tends to stick with you too, sorta like a tattoo.
So it could be that they would take your hard-earned money and check things on your motor but not blow out or clean the pilot jet specifically.
I currently have six outboards: 2 Hondas (15hp with electric start and tilt), the old 7.5), Three tohatsu's (an 8, a 6hp sailpro and a 3.5hp twostroke) and an old 1950s Evenrude that is partially made of brass for saltwater operation. This isn't all I have HAD, just my current herd. The old Honda is the most worrysome. The 15hp is a dream. The two new 4-stroke Tohatsu's are too new for a verdict, but so far the bench tests are good, prior owners report them as fine motors and the rumors are they will be good.
Ok, nuff said. Good luck with this.