1986 Yamaha 40HP Questions

[tgarrity]

Two questions:<br /><br />- Does anyone know if this motor has a built-in pitot tube for a speedometer? I guess most of them do nowadays, but given the age (1986)?<br /><br />- Engine runs pretty rough at low speed--shakes entire pontoon. I'm new to outboards, is this normal for a 2 stroke? I understand they "load up" at low speeds and don't like to be run slow. Carbs were removed and cleaned professionally this spring. Mech said they were gunked up bad. Plugs were replaced at that time also.<br /><br />Thanks!<br /><br />Terry

 

[jim dozier]

Re: 1986 Yamaha 40HP Questions

The answer to question 2 is, no 2-strokes aren't supposed to behave like that. You have something amis probably in either the ignition or fuel system. Start pulling plug wires 1 at a time and see if you can find a cylinder that isn't firing (best to ground the unattached wire). Then check to see if that cylinder has a good strong spark. If so gotta be fuel <br />-carbs (maybe not properly fixed)<br />-fuel pump <br />-air leaks in fuel lines or gaskets