I do not have specific experience with the Tohatsu propane but, I have had the Lehr 3.5Hp for several years and can report on that. In general, I find that the propane is a good solution for occasional use. It has been reliable and not subject to the gumming and other maintenance problems of my previous Tohatsu 2cycle. Unfortunately, Lehr is no longer in business. My question would be whether your FS can handle the weight and power of a 5HP. Check with Flying Scot for their recommendation on that.