Mine used 25 to 1 also. The best thing I saw was in the operation manual that I got with it. It said something like, “use the cheapest fuel you can find”. I did and it ran great.

I was told that they were originally designed for the British Secret service to be used in covert beach assault. It was used to bring them to the beach, then the boat and motor could be sunk just off shore so it would not be seen. Then recovered for the return trip.

Greg