On a recent 5-day trip on the water to Catalina Island, my 150 hp. carbureted Yamaha began running rough at low speeds only, sounding like it was missing, and lacked power until mid-throttle, then would "break free" into high and smooth running. I don't know if its related or not, but when I got the boat off the water and home for cleaning I noticed what looks like a vacuum tube running down from the head to the lower unit, and it had separated. Does anyone know what the function of this tube is, and could it possibly be the source of the problem? I haven't run the boat in the water since reconnecting the tube, but was just wondering if anyone else has had a problem with low rpm function due to vacuum leak.
I did see a similar problem discussed, and the conclusion was that it was a fuel diaphragm?
I did see a similar problem discussed, and the conclusion was that it was a fuel diaphragm?