It just doesn't run right-200 Merc

Well, If anybody can help I'd appreciate it. I have two problems, don't know if they're related or not. Prob 1. Runs real rough starting around 1000, clears out about 2000. It's as if one cyl is not firing or like one cyl is so far advanced it's trying to run backwards. (makes for very uncomfortable trolling!
Prob 2. It will run 4600 all day and it will run 5600 (45-48mph) for 30 sec to 2 minutes. Then it quits like it is fuel starved. If I pull back the throttle to neutral it usually keeps running and after 30 sec to a minute I can run again (up to about 4600).
Now, I just got it back from a mechanic who rebuilt the carbs and fixed a third problem (flooding and skipping on one or more cyl at high speed). These other two still exist. Wk before last in the gulf I shut it off when it "quit" at high speed, pulled the plugs and saw 1 bank was clean and the other was dirty. Hot Dog! it must be the switchbox! Wrong. I tried a new one on port and then rotated to starboard with no difference. I run off three different tanks w/two hoses/bulbs--no difference. Comp is 120 on all. All check valves to the bleed hoses work. All main jets are OK. I'm spending more money on plugs than gas. I've changed the impeller and running about 20psi at 4500 to 5000. Have a stream out the tell tale. The stator was replaced last year. I do get a "healthy" spark on all plugs/cylinders at cranking speed. Etc., Etc.
Any ideas? ???
Trollercoaster

[macojoe]

Fuel delivery??

Vents, hoses, bulb, Orings, filters, fuel pump???

Fuel bulb is full and tight even when it quits at high speed. (I thought sure that was it for a long time). "Rebuilt" the fuel pump as a possible cause--no change.

How about the stator? Or, how about that little box on top for extra advance at 5600 and up?
Thanks,
Trollercoaster

[bigshrimpin]

Describe the plugs or take some pics . . . when you say clean and dirty . . . I'm not sure what your mean?

What year is the motor? 2.4L or 2.5L

When I checked this once after engine shutting down in high speed run, the starboard side plugs looked "normal" like they'd been dipped in dirty motor oil with a little brn/blk surface deposits which I could wipe off. The port side looked like they'd been rinsed in clean fuel-oil mix. I thought that would point to the port side switchbox, quitting due to a heat breakdown problem. Also, at least once, after idling/flushing engine, #4 plug also looked clean while all the others looked like they'd been firing.

Trollercoaster

[spareparts]

change out both switch boxes, the bias circut can cause a problem with the other box, even if ther is nothing wrong with it, allways change both boxes, if one fails, the other isn't far behind

i have heard lots of bad things about merc over the years. but, even the biggest haters have to admit that the newer motors are much better. but, in my opinion, they are still black, and a nazi just dont wanna work! good luck!

You do have to change both power packs like Spareparts said. Mine did the same thing and it turned out to be the stator. Get a manual, it will tell you how test it with meter.

;DHappy day! I can't find the poster who suggested to get rid of the little black box (high speed advance) but that was the problem with the cutting out above 4600. Thank you for sharing your extreme knowledge! It ran great at high speed, at 5200 as long as i wanted (10-15 minutes). It would hit between 56 and 5800 and when I slammed it all the way down from 4000 or so, it jumped!
I still have a rough spot between 1-2000 which I suspect may be a coil. It's not real obvious which cyl is weak. I guess I'll have to run it for a while at 1500, then cut it off, pull the plugs and see which one looks like it's not firing, unless somebody has a better idea?? It'll be March before I see it again. ;D

Thanks, Trollercoaster

[phester]

might it have been Bigshrimpin??? He's a Merc motorhead