I've recently begun to research and price alternatives to the common tender 4 stroke outboard. In my research I came across a few interesting candidates. One being the "Torqeedo"
this little outboard comes in Horse power 🐴 from 2.5 - 15. Also you can use the small camping ⛺ canisters or connect up to a 40lb. Tank with the provided hose.
It was while researching this engine I came across this little video https://www.youtube.com/watch?v=uDoBBxa0jIo
this is now my current "side" mission, to either buy or convert my zero hour 9.9 Yamaha to propane. I have found a few places that sell conversion kits for all manor of engine, from gensets to 6 cylinder cars.