I recently bought a 6hp 1970's evinrude for 150$. I took it for a rip on my 12ft aluminum boat, the motor starts first pull, idles perfect, accelerates like a top and can maintain top speed without any issue. The problems arise when I try to hit the lower speeds that I'd like to troll at it will cough for about a minute and then eventually cut out and I have not a clue what I should do to resolve this issue I'm new to outboards and looking for anyone's input on the matter thank you for your time and hope to hear back from some of you.