Honda Guy Here...
Hi Robert, and thanks for starting this thread. I have a fairly new Honda 5-HP 4-stroke outboard on my sailboat. It's very thrifty on fuel but has one major disappointing drawback - if left sitting for 4-weeks or so, the carb gums up and it will either fail to start or run very rough. This is a very common, recurring problem that leaves me questioning my choice of motor. My dealer says that the low speed jets in the carb are really small and prone to fouling. I always disconnect the fuel line and let the engine run out of fuel after each use. Our Arizona summer temperatures likely hasten the break-down of the fuel and the creation of gum and varnish deposits.
Starting in June, I've been running LL100 aviation gas in it, and it has gone 6-weeks between uses and still starts and runs well.
Is this the answer to my problem - av gas? Is there a better answer? Is there any downside to using av gas? Yes, it's expensive; but, I haven't missed any sailing days since using it, and it's cheaper than having my carb cleaned several times a year.
Thanks for any info that you can share.