I have a 1979 6hp Evinrude motor with a grip throttle. I would like to tighten the throttle so when I'm trolling I don't have to keep holding the grip. This motor always idles down to the lowest idle speed when you take your hand off the grip. Is there a way to tighten something in the handle to get the throttle to stay at the desired trolling speed or is there an adjustment near the cam follower that controls the throttle tension.