Remove Choke on Merc 140

[myoldboat2]

I'm going to try my Merc 140 with the choke plate removed. The messed up choke also sets the fast idle cam incorrectly when the engine is warm. I set my warm-up RPM manually anyway. What's the best way to fix the idle setting... fix the cam in place with a serrated lock washer or remove the cam and use a very long idle screw? If someone has done this, I'd appreciate hearing how you handled it. Thanks.

 

[Bt Doctur]

Re: Remove Choke on Merc 140

You really should leave it alone,once properly adjusted, it will work fine. Tell us why you feel it`s not working properly.

 

[myoldboat2]

Re: Remove Choke on Merc 140

Choke plate is set correctly when cold, almost closed, then opens quickly as the engine warms, then after 1 hour pulling skiers choke plate closes tightly. No idea why it does this. Lots of details in this thread (which I don't think anyone reads any more!)

 

[Bifflefan]

Re: Remove Choke on Merc 140

If you MUST mess with it then, on the other side from the pic is a black plastic round plate with 3 screws locking it down. Loosen the screws and rotate the plate clockwise until the clock opens fully then go just a tad more and retighten the screws again.
This will effectivly take the chock out of the operation. and then when you decide you need it again just reverse the process.

Mark the plate BRFORE you move it so you can go back to the orginal spot again later.

 

[ziggy]

Re: Remove Choke on Merc 140

seems to me bifflefan would be onto a good way to do that.

i read your thread. seemed like there were some good insight on there to me... i still wonder if your carb ain't doing this..

normal and proper..

not normal and not proper. the cam should not be able to move to the wrong side. i believe my carb is worn. this carb when it was last used, if i remember right, did just what yours does. the choke would stay closed, on mine, intermittently. when it failed the choke plate would feel solid and not open.. i'm not running this carb now..

on my 75, the coke cover is set to index mark per spec. almost intuitive... amazing...

 

[myoldboat2]

Re: Remove Choke on Merc 140

I've ran it with set to the index mark per spec and also turned well clockwise of that, same result--it ends up with the plate tightly closed after towing skiers. This time I did look at the high idle cam, but after I had pushed on the choke plate a few times. It didn't look reversed. I think my vertical choke rod (or the slotted cam hole) is worn, too, because once in a great while the lower end will pop out of the cam hole. This is not when the plate is shut tight.

Anyway, I'd rather just figure out what to do with the idle cam and try it with the choke plate off. Ideas?

 

[myoldboat2]

Re: Remove Choke on Merc 140

I found the old 2GC carb manuals at the Old Car Manual Project website. There's a good description of the operation of the Model 2GC Choke System on page 8 of the 1964 manual. It gives me a better understanding of the choke, but I still don't understand why mine is closing tightly after towing skiers.

As much as I hate to do it, maybe it's time to throw some parts at the choke. Maybe a new thermostatic coil, new fast idle cam and new vertical choke rod. Of course, I have no idea where to get new parts.

So I'll probably try it without the choke plate like Charlie suggested. Just not sure what to do with the high idle cam.

 

[Silvertip]

Re: Remove Choke on Merc 140

You've muddled with everything in the choke system -- all of it wrong. You NEVER set the choke on a warm engine. Set it on a stone cold engine. Hold the throttle open a bit, loosen the three choke adjustment plate screws and rotate the plate so the choke opens a bit, then go the other way until it just barely closes - not almost closed, "closed". Tighten the screws. Now try it. When the engine starts the choke should pull open a bit and then progressively open as the choke coil warms up. When fully warmed up the plate should be perfectly vertical. Since the carb has been worked on, it is possible you have something in the linkage reversed -- the choke coil is backwards on the plastic plate, the tab for the internal choke pull-off is not hooked to the choke spring. These are just a few possibilities.

 

[myoldboat2]

Re: Remove Choke on Merc 140

I've set the choke probably six times now, most of them with the engine cold.

> When the engine starts the choke should pull open a bit and then progressively open as the choke coil warms up. When fully warmed up the plate should be perfectly vertical.

That's exactly what it does until I pull a skier for about an hour. Then I find the choke plate closed very tightly. I can push it open and it's a strong spring feel, it closes again tightly.

The problem started before the carb was recently worked on. The choke coil is on correctly, pulls the choke plate closed when cold. The coil is engaging on the tab when the choke is set and during warm up.

 

[Silvertip]

Re: Remove Choke on Merc 140

Then identify the spring that is forcing the choke closed when warm. If this is happening after an hours run, the engine should be running poorly. Or is the choke closing after you've stopped for a spell?

 

[bigskiohio]

Re: Remove Choke on Merc 140

as long as you boat in the warm season choke not needed. just pump it 3-4 times and let it warm up.

 

[ziggy]

Re: Remove Choke on Merc 140

That's exactly what it does until I pull a skier for about an hour. Then I find the choke plate closed very tightly. I can push it open and it's a strong spring feel, it closes again tightly.

just out of curiosity, have you checked to see if my not normal, not proper condition is applying in your case? after the failure occurs. if ya have. i'll leave my only wag be and hope others can help you find it.. it just strikes me a odd that your choke is giving similar failure as mine did. + this choke system on a 2gc don't seem that complicated as carbs go. not much to fail... good luck man..

 

[myoldboat2]

Re: Remove Choke on Merc 140

Then identify the spring that is forcing the choke closed when warm. If this is happening after an hours run, the engine should be running poorly. Or is the choke closing after you've stopped for a spell?

I'm 99% sure the spring is the thermostatic coil in the choke housing. When in the tightly closed condition, if I loosen the three cover screws, the cover spins CW to relieve the tension. By the time I get the cover open a bit to look inside, the tension is relieved. So I had been wondering if it's possible that my thermostatic spring is bad, and is coiling all the way around and engaging the tab for a second time--but that doesn't make much sense to me. Anyway that's why I thought maybe I should replace the coil. Is it possible that my 35 year old engine is dumping too much heat into the choke housing to cause the coil to expand way too much? I guess I should do a compression test, it's been a few years, but doing a compression test for a choke problem seems goofy.


> If this is happening after an hours run, the engine should be running poorly. Or is the choke closing after you've stopped for a spell?

The engine runs good until I shut it down and then try to restart it. I'm not sure exactly when the choke plate closes. This has happened about 4 or 5 times now, always when pulling skiers/wakeboarders. I haven't done that with the engine cover pulled and the flame arrestor off to watch the choke plate; wouldn't be comfortable doing that for 30 to 60 minutes or so.

 

[myoldboat2]

Re: Remove Choke on Merc 140

as long as you boat in the warm season choke not needed. just pump it 3-4 times and let it warm up.

That's what Charlie said, too. What should I do with the fast idle cam?

 

[myoldboat2]

Re: Remove Choke on Merc 140

just out of curiosity, have you checked to see if my not normal, not proper condition is applying in your case? after the failure occurs. if ya have. i'll leave my only wag be and hope others can help you find it.. it just strikes me a odd that your choke is giving similar failure as mine did. + this choke system on a 2gc don't seem that complicated as carbs go. not much to fail... good luck man..

I did look for the fast idle cam going the reverse direction, but it wasn't the last time this happened. I've only had it out the one time since you first suggested that problem, because it took me so long to find the fuel dumping problem and the leaky carb float.

 

[myoldboat2]

Re: Remove Choke on Merc 140

Thanks for all the ideas, I appreciate it. I really don't understand why this choke is closing tightly after it opened correctly during warm up.

 

[ErieRon]

Re: Remove Choke on Merc 140

I'm 99% sure the spring is the thermostatic coil in the choke housing. When in the tightly closed condition, if I loosen the three cover screws, the cover spins CW to relieve the tension. By the time I get the cover open a bit to look inside, the tension is relieved. So I had been wondering if it's possible that my thermostatic spring is bad, and is coiling all the way around and engaging the tab for a second time--but that doesn't make much sense to me.

I have the same carb/choke. I suspected a problem in the spring and found that the center screw holding the spring coil had fallen out (obvious problem). Since I had it open, I removed the entire choke and bench mounted it in a small vise. I put 12 V to it and watched the spring to verify that it was good. My recollection is that it only moved about 35-45 degrees, which in my mind was about right, just enough to open the choke. When I reinstalled it, I did so with only slight tension on the spring, relative to the cam...no winding tight. I haven't had any problems since. Point is, it was a very good learning experience to watch it work on the bench, so I understood how it was effecting the carb. Hope this helps.

 

[fat fanny]

Re: Remove Choke on Merc 140

Erieron what did you use for a power supply?

 

[myoldboat2]

Re: Remove Choke on Merc 140

I have the same carb/choke. I suspected a problem in the spring and found that the center screw holding the spring coil had fallen out (obvious problem). Since I had it open, I removed the entire choke and bench mounted it in a small vise. I put 12 V to it and watched the spring to verify that it was good. My recollection is that it only moved about 35-45 degrees, which in my mind was about right, just enough to open the choke. When I reinstalled it, I did so with only slight tension on the spring, relative to the cam...no winding tight. I haven't had any problems since. Point is, it was a very good learning experience to watch it work on the bench, so I understood how it was effecting the carb. Hope this helps.

I agree with testing it as much as possible and watching the behavior. My choke is a thermal choke, not electric like yours. I've been wondering if it's somehow getting too much heat through the heat tube. Anyway, last time I had the choke apart, the spring was mounted tightly to the cover. I'll check it again the next time I pull it apart.

Back to the original question--if I remove the choke plate and the vertical choke rod (the one that goes to the high idle cam), what's the best way to handle the idle cam and idle speed screw?

Thanks.

 

[JustJason]

Re: Remove Choke on Merc 140

There shouldn't anything you have to do at all to the cam or speed screw.

Be forwarned though. The screws that hold the plate on are peened over. They were never meant to be removed, or fall out. Its a bear to do but i'm sure you can get the screws out. But once there out, thats it. Don't ever think about putting them back in. Because they will fall out and get injested by the motor.