I have a 1993 Evinrude 28 HP model E29ESLETD that won't run properly . With primer off the engine will start and sputter out after 1-3 seconds. If I turn the primer on (red switch near carb counterclockwise) then the engine will start, idle, and rev up in neutral just fine but will bog down when in forward gear. I can putt around but that's it. I have adjusted the mixture control to all settings (in/out) with same result. What is approx mix control setting? any thoughts on this issue? could it be a vacuum leak? should i try bypassing the primer all together? check for fuel in the float? maybe carb jets? boat has been sitting outside for aprox 6 months. I put in some new fuel.