This seems to be a fairly common problem on carbed v6's what do you guys think?

[pcrussell50]

From another forum:
Have a mercury 200 black max and no matter how warm the engine is it keeps dying at idle. I can raise the fast idle bar and keep it running, then push it down and go to fwd with the throttle quickly and it will run. Once i am going the motor runs great with no problems. But once i go back to idle the motor shuts down again. I have replaced the plugs, put on a new fuel filter and hve been running high test . Also every so often when comming out of the hole the enging will not rev up but once i move the throttle back and the go fwd it will work fine. I have also checked the carbs and the jets are as clean as they get. Thanks in advance for any help you can give

This is exactly what my carbureted, 1987 2.0L is doing as well. I have all the modules removed that you guys said to remove, like the idle stabilizer, and running 50:1 premix with the oiling system removed. Next spring, I will go through the carbs (even though I bet they are clean), install the CCM reeds I got last week, and check all the bleed lines and check valves, and rebuild the fuel pump. Other people have done the same thing, and still have the same problem as with here:

join the club from Kip (151.197.109.132)7/9/1999 12:45:00 PM
While not all Mercs have this problem, I think you'll find that of the ones that do, this problem is common. My '91 40 has this problem. The temporary cure is a high idle. I've been whittling away at this one all season long and have been paying attention to all the others on this board and at walleyecentral.com who have this problem. I've replaced everything at least once and have minimized this problem but I still can't get it to idle at 500-700 all day like it should be able to do.Problems found to date: dirt in fuel pump (rebuilt that), dirt in filter (replaced it), check valves sticking in new non-Merc bulb (replaced with Merc bulb), float levels low (rebuilt carbs and adjusted). Things are better, but not perfect.
This problem seems more common with the older motors, and it could also be a poor pressure pulse from the crankcase which operates the fuel pump (read: seals etc.). Newer motors seem to have better pumps. I know newer versions of my motor employ a different design which I may upgrade to but that will require powerhead removal and disassembly. Ideally, I'd like to install a small, low current draw 2 psi fuel pump to keep the engine primed at all times... but maybe I'm dreamin'.

This guy above is wondering if changing to an electric fuel pump might fix it. So am I. And I'm willing to try. What do you guys think? Or maybe the CCM reeds will give a stronger crank case pressure pulse at idle? It seems to run great off idle.

Can someone give me guidance as to what electric pump to get and how to wire it? I'm pretty handy with that stuff, just need a little shove in the right direction.

-Peter

[Go Time]

Pete, check the float levels in the carbs and make sure the idle air jets(if it has them) are the correct size. Check all the bleed line check valves too.

[Dave Strong]

Do the carbs and use new needle and seats, full link and sync. If the idle is low speed it up with the pick up timing until it is running good. As said above make sure it is jetted correct and bleed lines are routed correct and in good shape.

Dave

[tlwjkw]

make sure all tha link n sync stuff is as it should be then put it in tha water, in gear and adjust "idle timing" only ta get want ya want for tha idle speed and rpm... don't worry what tha book says for idle timing... if that doesn't work then ya may have a carb problem...

[daytrader]

Maybe I got lucky but when I switched to CCM reeds it finally let my 2.4 idle at about 750 in gear, maybe a little high but much better then the 1000 to 1100 I had to endure before.

[1BadAction]

It's common because a lot of these motors are 30+ years old and not many people want to fix **** the right way. They're worn slap out, people are half assing the carbs, messing with spark control when they don't totally understand how it operates, etc. If it will not idle at 750-800 RPM in gear, there's something wrong. Once you start getting away from the stock configuration (like deleting idle stabilizers), setting the idle is a compromise between high idle in neutral and stalling out in gear.

The real fix is computerized spark control, but that's a totally different subject.

[pcrussell50]

Re link'n'sync, the motor runs great right off idle, all the way to the top, with no bogging or soft spots.

The only problem this motor has is, it slowly dies at idle, and won't start unless the throttle lever is pushed forward like you do when you cold start or flooded. Then when its running, you have to keep it idled up and quickly throw it in gear and get off idle. The weird thing is, it idles for a while when cold, and idles for a while after running on plane, before finally dying. I wonder if maybe the fuel pump has trouble keeping up with the slower pulsing at idle. I noticed that the primer bulb is partly (but not completely) soft at idle too. Sounds like I may have to do my part and try squeezing the primer firm while trying to idle to see if that helps, just to check that box.

It's common because a lot of these motors are 30+ years old and not many people want to fix **** the right way. They're worn slap out, people are half assing the carbs, messing with spark control when they don't totally understand how it operates, etc.

I would hope that folks hanging out here are not too much the types to half-ass their V6 Mercs. I know that's why I post here before other places... Because I consider the expertise here, above all else.

If it will not idle at 750-800 RPM in gear, there's something wrong. Once you start getting away from the stock configuration (like deleting idle stabilizers), setting the idle is a compromise between high idle in neutral and stalling out in gear.

Based on 1BadAction's post above, maybe there actually is some value to the idle stabilizer? Or maybe I just rebuild the pump, clean the carbs, add in the CCM reeds I have sitting in a box, and bump the idle up till it doesn't die, and call it good?

Is there any merit to my thought that maybe at idle, pulses are too weak or infrequent to keep the bowls full enough? And that maybe after I throw in my CCM reeds, it might improve things a bit?

-Peter

[home made tunnel]

New reeds will do wonders. WHen you pull out the old ones, look and see if they're hanging open slightly. It only takes a little bit to screw your idle. At higher RPMs, you have a stronger pulse going from bottom of piston, back down to the reeds to slap them shut tight.

[1BadAction]

I would hope that folks hanging out here are not too much the types to half-ass their V6 Mercs. I know that's why I post here before other places... Because I consider the expertise here, above all else.



Based on 1BadAction's post above, maybe there actually is some value to the idle stabilizer? Or maybe I just rebuild the pump, clean the carbs, add in the CCM reeds I have sitting in a box, and bump the idle up till it doesn't die, and call it good?

Is there any merit to my thought that maybe at idle, pulses are too weak or infrequent to keep the bowls full enough? And that maybe after I throw in my CCM reeds, it might improve things a bit?

-Peter

Yea, I was referring mainly to "other forums" facebook, etc. and I agree, most of us will do it right unless we're trying to scab something together on a moments notice.

Once you get your reeds in there and revisit the issue, it may disappear completely.

[Steve Pope]

These engines are getting old. Is it just a simple case of worn out engines. Do a leak down test before you do anything else. If you have no ring seal then every other adjustment away from factory is just a compromise.

[Dave Strong]

These engines are getting old. Is it just a simple case of worn out engines. Do a leak down test before you do anything else. If you have no ring seal then every other adjustment away from factory is just a compromise.

People just don't know how to do a proper link and sync, as soon as things don't work they start looking at Bazar things and forget the basics. Suck, squeeze, bang, blow. If any not right it will not run well.

Dave

[pcrussell50]

These engines are getting old. Is it just a simple case of worn out engines. Do a leak down test before you do anything else. If you have no ring seal then every other adjustment away from factory is just a compromise.

You're right, mate. I probably should do a leak down test. It's just that it's run so nicely the last couple of years, until I tried to slow the idle down late this season, that I was never motivated to do it. Perhaps now I will... Just for peace of mind.

It looks like after I do the carbs, fuel pump, and install my CCM reeds, I'll just live with the best idle I can get... like everyone else.

-Peter