115 stumbles on takeoff

[btroy]

Hi guys have a question about my 77 inline 6 tower of power, Serial number is 4701195.

I rebuilt the carbs and the boat runs really well now. Only problem I have is when I shift into gear the motor stumbles and then dies. It will do this unless I play with the fuel enhancer to get it going.

My inital settings for the carbs were 1 1/2 turns out on each carb. It runs good at this setting, however I did turn each carb out an additional 1/8 turn just so I was not running too lean and take a chance of burning a piston.

Is this a good procedure I should stick with or should I turn the carbs back to 1 1/2 and then lean it out alittle more to get the stumble out of the engine when taking off?

I also rebuild the fuel pump and installed a new water impeller.

Any help would be appreciated.

BTW I did perform the Timing and Sync procedure.

Troy

 

[Silvertip]

Re: 115 stumbles on takeoff

Those are idle mixture screws and have no effect on high speed operation. 1-1/2 turns out is a rough setting. That is NOT the final setting. You need to fine tune the idle mixture on each carb to prevent what you are experiencing. That fine tuning also needs to be done in the water, not on muffs.

 

[btroy]

Re: 115 stumbles on takeoff

Those are idle mixture screws and have no effect on high speed operation. 1-1/2 turns out is a rough setting. That is NOT the final setting. You need to fine tune the idle mixture on each carb to prevent what you are experiencing. That fine tuning also needs to be done in the water, not on muffs.

It runs fine at WOT.

Yes I realize they are the idle mixture screws, so I guess I will just richen them up and play with it until it is ok.

Thanks

 

[Silvertip]

Re: 115 stumbles on takeoff

There is no "playing" with the screws. Adjust them properly and be done with it. How do you know the setting isn't already too rich -- or too lean for that matter.

 

[CharlieB]

Re: 115 stumbles on takeoff

Idle mixture MUST BE done IN THE WATER and IN FORWARD gear.

Idle mixture must be adjusted to BEST speed IN GEAR "PLUS" the additional amount needed for crisp acceleration. Oten this is 'about' 1/8 turn richer (out) from best idle.

Ideally, adjust to best speed PLUS the width of the screwdriver blade slot. Test acceleration by slamming the throttle control WOT, ANY lean cough, bog, or hesitation then turn idle mixture screws out an additional blade-width and retest acceleration. Repeat to perfection.