Re: 1977 evinrude warm-up lever
It sounds like what mine was doing. I had to tear the control box apart - was doing this because the key switch broke off. When I got the two halves apart, in the bottom laid a small piece of plastic. There is a "gear" in the control box that returns the warm up lever to nuetral before you can advance the throttle/shift lever. If this is what it is, it is easy to replace. The hard part is to find the part.
Even if this is not your problem, you are not wasting your time if you clean and grease everything. Mine was an 1986 and the grease inside wouldn't come off without scraping and soaking in redneck parts cleaner (gasoline). It was hard as concrete. If you decide to tear apart the "remote control", do youself a favor and take pictures with a digital camera on every step of the process. You will forget how it goes back together and the pictures are a godsend.