1977 mercury 850 won't get to WOT with out choke

[po-way]

1977 mercury 850 cranks with a touch,idles fine,trolls along good till about half throttle then bogs.Push the choke and hold it while pushing throttle till you get past that point and it will run WOT for miles.Once you back off past that half way spot you will have to push choke again to get back to wide open throttle.I've cleaned carbs.

 

[MH Hawker]

Have you tried pumping the ball

 

[po-way]

Pumping bulb makes no difference. Rebuilt fuel pump.

 

[Chris1956]

It is likely that your idle mixture is too lean. Richen the top carb 1/8 of a turn and retry acceleration. Follow with bottom carb and retest. Repeat sequence, until you achieve reasonable idle and good acceleration.

 

[po-way]

Thanks Chris1956. That's what I was thinking,had a similar problem last year. I had already backed off idle mix screws earlier today 1/8 turn on both carbs but will have to wait to put it back in the water to check it. You say I should only do one carb at a time?

 

[Chris1956]

Yes, do one carb at a time. The top carb runs a bit leaner than the bottom carb (due to gravity), so it will likely need the most richening.

 

[po-way]

Thanks again Chris1956.I've been fighting with this old merc for a while.Thought I had it at the end of last year but now it has started the same thing.I will give you a progress report when I get it back in the water.I appreciate the info.