Mercruiser 140 Hard Started and Idler question

Hi, I have an 83 mercruiser 140 inboard. I bin having problems with the engine starting warm and stalling while idling into dock. I have done a carb kit new cap, rotor, spark plugs, pionts, condenser. I lost my service manual and can seem to find idle rpm setting and idle screw mixture setting (how many turns they should be) Its just a 2 barrel carb. I'm a fairly handy guy but this boat is killing me. The choke seems to work fine. It smells like it flood itself. It runs great around 1200 plus rpm. Its smooth it that rpm range, but rough under it. What should it idle around? Also when its in the water it runs worst that it on land with muffs on. I was really dissapointed doing all this work and still seem to be haveing the same issues. Can anyone offer me a few pointers to help me out. I sure don't want to buy another manual. Thanks

Re: Mercruiser 140 Hard Started and Idler question

Run your idle air mixture screw all the way in carefully!! DOnt crank it tight just go till you feel slight resistance. Then back it out 1.5 turns that is a good start point. Idle needs to be set in the water in gear. Should be at 650-700 rpms. On muffs it could be as much as 100 rpm higher due to no back pressure on the exhaust.

Re: Mercruiser 140 Hard Started and Idler question

cooter2506 said:

Then back it out 1.5 turns that is a good start point. Idle needs to be set in the water in gear.

Click to expand...

That IS a good start point, but is not the finish point.

You really need a vacuum gauge to adjust your mixture screws. When you buy a vacuum gauge they generally come with pretty good directions for setting your air mixture screw(s).

Re: Mercruiser 140 Hard Started and Idler question

I have a vacuum gauge but have no idea where to put it on that engine. I can't see that motor running at 650 rpm in gear. I do have the idle screws maybe a bit far out. I will check it out. Thanks

Re: Mercruiser 140 Hard Started and Idler question

Anymore suggestions? Thanks

Re: Mercruiser 140 Hard Started and Idler question

Hi, still having problems. I took it on a fishing trip for five days. It always started hard. It runs on the starter till about 800 rpm then I can finally get it going. I usually run the battery down to get it to start. When started it only runs good around 1200 rpm. I know the linkage is out on the shift interrupt switch. It doesn't stop the engine to shift, but I know the switch works cause i can manually move it to kill the engine. The boat will sometimes run up to 2000 rpm on idle. When it runs that high I can turn the ignition off then back on again after about a second. The rpms drop and will stay around 1200 rpm. Then they will slowly rise sometimes. I know thats a little bit of linkage issues. But the boat shouldn't start running on lower rpm when I turn the key off and on again. Could this possibly just the carb is worn out. I did rebuild it. It runs great at above 1000 rpm. Its has lots of power and runs good full out. I even ran premium gas in it. Can it be a week coil. That boat use to start and run good. The last 4 years has been giving me problems. I did the points, condencer, wires, rotor, cap, plugs, carb kit. I don't know what else to do. I really don't want to take it in because the bill will higher than what the boat is worth. I figure I'm a handy guy with engines, but this thing is killing me. Its a 140 mercruiser 4 cyc. 2 barrel carb. How much will timing affect the starting. I never checked it this yesr but it runs good other than starting and idle. I just have to keep it idling higher but thats hard on the gears when shifting. Any more help would be welcome. I'm ready to sink it. Thanks

Re: Mercruiser 140 Hard Started and Idler question

Just bumping post back up. Help please

Re: Mercruiser 140 Hard Started and Idler question

A couple of thoughts. It could be your idle circuit is still plugged on the carb - that is a different circuit than an open throttle situation.

You say you replaced the points, etc but haven't timed it in awhile. Everytime you replace the points you affect the timing and it should be checked. I doubt that is your problem, but it is something to check.

Re: Mercruiser 140 Hard Started and Idler question

the 140 is the 3.0L even for an 83, I think. If so, your intake maniford will have a brass screw-in plug on the top of it (just stern of the carb). That is where you connect the vacuum gauge. Your gauge should have an adapter to fit that spot, if not, just head to your nearest plumbing place for an adapter. Once running, adjust the timing first, then your carb. It sounds as though your carb may be flooding (float adjusted too far down), but your timing should always be set before you ever touch your carb.

Here is a GREAT site for using a vacuum gauge: http://www.secondchancegarage.com/public/186.cfm

Don't skimp on getting your engine runnign correctly. Replacing it costs MUCH more.

Re: Mercruiser 140 Hard Started and Idler question

Thanks for all the replies. I think I found it. I never checked it because I rebuilt the engine 5 years ago and it has few hours on it. It has low compression on one hole. Thats got to be it. Now to find out why. Looks like I'm pulling her again.