When I put Seafaom in my 1991 40HP Evinrude, the idle runs higher that when Im not using it. I am putting about ½ of a can in 12 gallons of gas. After the seafoam gas runs out it will idle slower. I don't have a tach, but I can tell is running much higher. It's almost high enough for an on the water idle adjustment. <br />Has anyone else had this happen? 