Like the title says I have a 115 tower of power. It is a little tough to get started and when it does start there is a clacking noise. When you rev it up it goes away, and when its warm its not as bad at an idle but still bad. It will kill the motor when its cold, so you have to rev it up and then quick put it in gear... what is it??? Also it isn't like a backfire or a cough like a johnson, and its not quite like a rod knock. The best way to describe it is it is a clacking sound... sounds like metal, but yet it goes away when revved up.