3.0 Mercarb Adjustment after rebuild

[bebecker]

I rebuilt my 2 barrel mercarb spring needle, factory specs, set the idle speed, and have the idle mixture set about 1 1/2 turns out. I am very happy with the improved starting as it was leaking before rebuild.

However, the engine bogs as it never has before when pushing (not punching) the throttle. I now bogs under load when pulling. My top end rpm has suffered as well.

There are only three things to adjust, idle speed, idle mixture, and float level. This carb does not have the three notches for the accelerator pump.

Could my problems be caused by improper idle mixture? Could my problems be caused by a low fuel level in the bowl requirng float adjustment?

I have done searched the form, it seems all questions suggest other problems or rebuilding the carb. I have done both (new engine, EST, timing set right). Your suggestions are appreciated.

 

[north 140]

Re: 3.0 Mercarb Adjustment after rebuild

Hello !!! I have to say thta I have the same thing going on with my 1981 140mercruiser 4 cl 3 litre. I replaced the plug, wires, distributer cap, both fuel filters, rebuilt the carb(helped), replaced my impellar(was shattered) new high octane gas, and still when I put it in gear and put her about half throttle it bogs out aand finally stalls. I have good spark in all lines and good fuel tank ventage. What else could it be?

 

[Reel Poor]

Re: 3.0 Mercarb Adjustment after rebuild

bb....Have someone operate the throttle for you. With the engine off look into the throat of the carb and see if the accelerator pump is working like it should. As the throttle is pushed forward (in the same manner you described problem) you should see a steady stream of fuel being squirted into the throat of the carb. If you don't see the fuel it's either a bad accelerator pump, faulty or missing pump check ball, of float level set wrong (to low).

 

[Reel Poor]

Re: 3.0 Mercarb Adjustment after rebuild

north 140....You should start your own thread instead of tagging on to someone elses. You will get more and better responses that way.

 

[enn858]

Re: 3.0 Mercarb Adjustment after rebuild

Had the same problem on my 2007 175 BR w Mercruiser 135. Took it to the dealer - only to discover i knew more about the engine than he did.

I read the original Mercruiser manual and

1)removed the anti tamper devise on the idle mixture screw - adjusted it app 1/2 out and the problem was gone (thank you to Don - he have made a post about this issue)

2) I adjusted valves

and

3)checked ignition timing (engine was 2 `off ) it was like getting a completely other engine -now that little engine accelerate smoothly and idles great - seems like these engines are runing lean at idle witch also causes a little bog a little at slow acceleration. When adjusting idle mixture make shure to follow the procedure in the Mercruiser service manual

So my advise would be to adjust valves ignition timing - and adjust idle mixture on your engine