I have been using SeaFoam in all of my gas/diesel powered equipment for over 18 years and never have I had anything but good results with this product. With the government mandated Ethanol in fuels today, it is necessary to have a lubricant added. My John Boat, Ski boat, motorcycle, Truck, wife's truck, daughters car, sons truck, tractors, riding mowers, generator and hand held gas powered yard tools all have SeaFoam running through them.
What I find most interesting about this thread is that just Sunday afternoon, one of my good friends became a believer in SeaFoam. We were out on the river in our John boats, and neither had run in a while. Mine cranked like I had run it yesterday, we had to jump his off when he drained his battery. His engine ran rough (even though he had fresh gas in his tank) and he could not even get up to speed. I asked him if he added any SeaFoam when he filled up. He said no. Well, I just so happened to have a can in my truck. We put that in his tank, gave it a good shaking, drained his fuel line, re-primed and got him running again. After about 10 mins of running on the river, you could hear the pitch of his motor change and he started running better. By the time we got back to the boat ramp, it sounded and performed like he hung a new motor on the back of his boat.
I have had similar results from an old truck my son got from his grandpa and my old Ford 9N tractor I bought from an estate sale.
Yes, it is a little pricey, but I would not store my equipment without it and certainly will not run my boats unless it is in the tank.