The propane engine runs on a different ignition curve than gas so a conversion lacking the ignition changes would not run properly. But it would run. You could just adjust the timing until you achieved the best results.
For my rubber duckie the very light gas 2 stroke Yamaha works well. I don't think we had alcohol in our gas in Alaska ... haven't had any storage and crud in the carbs but I know we have alcohol here in Wash state so I may be interested in propane in the future. I've seen the propane OBs at Harbor Marine in Everett WA. What I more likely will want propane for is a get home OB.
North Western Washington State USA