91 Merc 40hp 4cy 2 carb....tweaking carbs.

[mcdye]

I have totally cleaned the carbs which did make a differnce in the running, but I am still not getting the top speed like it use to. I would be running 25 and out of the blue it would kick in run the norm of 32mph. I did try pumping the bulb during the 25 speed and did not help. My questions is what adjusts on the carbs would help the top end be consitant and smooth? Smooth as in while on the 32 it seems to surge at that speed. Also how to you adjust or confirm the float level? The floats are plastic and the only option I see to adjust is to bend the tab that is holding the inlet valve. Currently they both appear to be slightly bent up when looking at the carb as mounted.<br /><br />Plus is there any other adjustments on the carb other then the floats and idle mixture?<br /><br />Thanks,<br />New forum vistor

 

[jim dozier]

Re: 91 Merc 40hp 4cy 2 carb....tweaking carbs.

When you cleaned the carbs did you clean ALL of the orifices and jets with carb cleaner AND compressed air? Did you install a rebuild kit? Dit you set the synchronization between the carb throttle linkage and the ignition timing advance linkage. Try choking the engine and see if that helps. Report the results back to the forum. It may also be that you have electrical problems in the ignition. Does the speed jump up quickly or does it sort of drift up and down?<br /><br />Go to the bottom of this web page and buy a manual for your engine.

 

[rverano]

Re: 91 Merc 40hp 4cy 2 carb....tweaking carbs.

Try and get a manual on your motor for what the float measurements should be. You can adjust the idle mixture screw on the carbs to get them tuned in right. Also check the secondary pickup on the throttle linkage. Sometimes it is not adjusted correctly and does not open the throttle plates all the way. Loot into the carbs, are they open all the way when you are at full throttle?