Mercruiser 140 Carb Help/Assembly Diagram Needed

[EBunny]

I recently bought a boat that has a Mercruiser 140, 4 cylinder engine in it. When I test drove it, it would hesitate on acceleration. As long as you eased into it, it ran fan, but accelerate to fast and it would bog. I bought it from a guy who is the service manager at a big boat shop. He is not a mechanic, however, his mechanic told him it needed a carb kit. When I bought it, he handed a rebuild kit from mercruiser for it. I have taken the boat out twice, once with Seafoam, and it still runs this way so I decided to do the rebuild. I have done rebuilds before on carbs with no trouble, however, when I opened up this carb, it looked to be clean as a whistle. Still, since I had gone this far, I said I would do it anyway, could be a leaking gasket or needle. Well I have it totally disassembled and started comparing new parts to old. All is the same except there are two little ball bearings that are not exactly the same size as the old ones. Is this a problem? Also, I have a brass rod that is about 3/8" long and 1/8" wide with straight sides no button head or anything. It came in the bag marked as 31-744 07E5 that contained the needle valve for the float, the spring for the valve, along with the small shaft with the button head and some sort of jet looking part. This brass shaft fit into the jet looking deal nicely, however mine did not have that when I pulled it out. It doesn't go with the needle valve as the other shaft goes with it. Does anyone have an assembly diagram for this carb, or can anyone tell me where this part goes?

Thanks in Advance!

 

[iowa_guy_45]

Re: Mercruiser 140 Carb Help/Assembly Diagram Needed

What year is this boat? I have a 1986 Mecruiser 170hp (4cyl) and rebuilt the Carb pretty easy, if it is a two barrel Rochester carb. Some things to make sure you do when rebuilding, make sure you put the disassembled parts in a some kind of cleaner solution and blow dry with compressed air, concentrating on the small air passages. Make sure you REPLACE the accelerator pump because this is probably your problem. Make sure you adjust the float level and float drop, but finding the specs for that may be hard.. I had the identical problem with mine, hesitation during hard acceleration, and the rebuild did the trick. I do have a diagram for the two barrel Rochester carb and the Mercarb Two Barrel one of those should be your carb if your motor is a 1986-1994, so if that?s what you have I could e mail you a scan of it. If fixing the carb doesn?t help I would replace the ignition points being sure the gap is correct, and after the points are installed and set check and adjust the timing?.Hope this helps

check your instant message

 

[supercab78]

Re: Mercruiser 140 Carb Help/Assembly Diagram Needed

Service bulletin said in my rebuild kit to use the spring & small pin in the needle IF you have a flooding problem at idle on 4 cylinder engines. Using the spring calls for a different float leval. The older carbs use a smaller accell pump plunger then the newer ones also. I had the same issues as you, bad weak accel pump, after doing the rebuild things got worse for me. I think it's because I used the spring & pin in the needle, with thier spec'ed float leval. I switched back and plan to test run today.

 

[EBunny]

Re: Mercruiser 140 Carb Help/Assembly Diagram Needed

Guys,

Found out shortly from a local marine shop that the solid brass rod is what was original. The spring and the button rod are what are suggested and yes you are correct that they require a different float setting. Mine was a Mercarb. I've got it soaking now. I also located some paper work that comes with rebuild kits and it shows the assembly diagram as well as gives float settings. I hope this works. I am ready for the lake but my boat is not. I am going to change the oil as I think when my pump went out, I got it to hot and broke down the oil. Luckily, I did not seem to hurt the engine. It got to about 220 degrees with only about three of the blades on the pump remaining. Anybody know what type of oil to run. Also, how about checking the water fuel seperator? I need a manual bad.

Thanks

 

[ziggy]

Re: Mercruiser 140 Carb Help/Assembly Diagram Needed

i just rebuilt my carb successfully. i used a mercruiser service manual for the specs..... you may find the info ya need here... http://forums.iboats.com/showthread.php?t=251571

 

[supercab78]

Re: Mercruiser 140 Carb Help/Assembly Diagram Needed

EBunny; I got back from the test run and finally mine is running good. I thought I'd let you know in case you have the same issues as me, that I had to use the SOLID pin with float set at 3/8 in order to get it to run correct. In my carb kit it said to set float at 9/16 when using the spring/pin set. With that set up, no matter how I adjusted the idle screw I had irregular idle and terrible take off from a dead stop, unless I just gave it full throttle. Once it was past 2000 RPM it run just fine and had good throttle response. I have a 1984 140hp merc.