15 HP Mariner Hard Starting

[bigboat606]

My 2006 15 HP Mariner has become very hard to star but It idles great once warm. When starting the engine cold, one pull produces a few engine fires, then stops. (Warm it starts perfectly - first pull.) Cold I have to give the engine a considerable amount of throttle to get it started. By considerable I mean I remove the cowling and advance the throttle by opening the butterfly valve on the carburetor several degrees. This allows the engine to start but runs very rough while keeping the throttle advanced. If I reduce the throttle the engine will sputter out and stop. The throttle once again must be advanced to start even though it has run for a short while (still cold). Once warmed up the engine idles good with only an occasional miss or sputter. Note I have reviewed the starting procedures priming the carb 3-4 times before starting (I tried more priming - no improvement). I also removed the carb to check the priming pump. It works great - shoots fuel four feet! Also I have checked the timing - its good. Is there an area of the carb I should recheck (clean) which controls cold starting other than the primer pump? Any ideas?

 

[flyingscott]

If you have the primer knob that controls the idle make sure the plastic parts on the advance are not broken. Turn the knob and make sure everything is being pulled like it is supposed to. If something broke in there it will not operate correctly.

 

[bigboat606]

Yes, I have checked the timing advance linkage and it seams to work correctly. I have even 'played' with it a bit by moving the advance linkage with my hand to see if the rough running when cold would improve. It did not. I'm leaning toward a carb rebuild, but hate to dive into a fix without understanding the problem.