I have a new 2020 Honda Baaj 8 HP , I have broken the engine in and now want to troll . I got a hour / Tach and installed it yesterday. After the engine is warmed up it idles at 840-850 RPM. Is there a adjustment to lower the idle ? I wanted to troll at .5 -.8 MPH and with the throttle all the way back at idle the boat trolls at 1.1 MPH. The Propeller that is on it is a 10/6.5 . If I have to change the propeller to go slower at the same RPM which pitch should I get ?