I never knew it existed. A friend of mine that is a marine mechanic mentioned it to me. I was getting 750rpm idle on my port motor longer that my star. It would take a long time for it to kick down after warm. He said to check my Muffler in my throttle body? Huh..Well I did and this is what it looks like. 420hrs, replace yours guys. Cost me $3 for both motors. https://www.wholesalemarine.com/muf...h4fcl8QHDzWsUmu5pWJ_872STTnAxVpQaAgC7EALw_wcB Gotta clean those blades too..