It just doesn't run right-200 Merc

[trollercoaster]

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???

[trollercoaster]

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

[trollercoaster]

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

[racerx]

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!

[8barrel]

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.

[trollercoaster]

;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

[macojoe]

Wow two of us getting the boat fixed in the same day!!

Good Luck!

[spareparts]

sounds like the low speed windings in the stator are going out,

Maco, did you get yours fixed also?

[macojoe]

spareparts, check repair thread for update ;)

[spareparts]

saw that after i allready had posted, couldn't find that manual, its around here somewhere

[bigshrimpin]

Troller - Glad to see you mostly fixed up there!! It's a great feeling when you yank that advance and your motor roars over 6K. You never knew all that power was hiding behind that little box. Dump that oil injection too and premix before it screws you over.

http://www.rickracers.com/product_info.php?products_id=3536

[bigshrimpin]

If it's not the coil or the stator . . . .the idle problem could be your reeds. If you've got the typical older Merc sneeze . . . try adjusting the tilt and make sure the motor is level (or at least tilted down). My motor idles real rough when it's cold.

What model carbs are you running?

[trollercoaster]

:-/ It kinda idles OK but seems weak on one cyl. Just when it gets under load around 900 to 1000, you can feel that steady spot up to about 2000 when it clears out. Trolling at about 6 to 7 mph takes about 1200rpm and you really feel it. The carbs are the W28's and I know about the larger jets on 2 and 5 but I also am up .002 on 1 and 6 because they have been bored and sleeved and the shop recommended I go larger on those because "they run hotter". The roughest spot is around 1500 to 2000 when it starts thinking about getting on a plane. I have a new spare coil. I just am having trouble locating which cyl is weak.

Trollercoaster :-/

[randlemanboater]

Something I have done when searching for a skipping cylinder is to disconnect the spark plug wires one by one. *When you unplug good cylinders, the skip will be much worse, when you unplug the bad one, there will be little or no change. *

I reccomend turning off the engine between each test so you dont get zapped.

And dont run it too long or you will gum up your good cylinders.

The other way I have used is simply pulling the spark plugs after running the engine, the bad cylinder should be drenched in gas/oil, as long as your issue is not a fuel issue.

Hope this hasn't been covered already, I didnt read the whole thread.

[randlemanboater]

I have owned two mercury ob's, wish I had them both still, they are great motors. One was a 1984 115 hp, the other a 1987 45hp. You could look at the key and they would start.

[Blue_Runner]

I've never owned a merc, but always heard they start easy.

[reelapeelin]

Never had a Merc, but did have a 40 hp Mariner elec. start ... never had a single problem of any kind from that motor... 8) ...

[bcmarinamanager]

i love my 200hp Merc. It's a '92 and I had a very similar problem running over 4000 rpm. My prob was the fuelpump though. sounded like it was doing the exact same thing yours was. Mine also runs kinda rough at the lower rpm range, not so much at trolling speed, but mid range, it sounds like it want s to run on out, and then cut back. can't find anyhting wrong with though. i just run with it. By the way, you definitely need to ditch the oil injection. Much Much safer.

[jared]

I would make sure that the throttle plates are sycronized, alot of the time when people redo the carbs they will not adjust the throttle plate, this causes some cylinders to get more throttle advance than tha others, the engine will troll rough, cough spit and die at idle. take the front cover off of the carbs, loosen the throttle plate screws, then flick each throttle plate and make sure it is shutting all the way, once you get them all the way shut tighten the throttle plate screws and recheck that all of them are are shut all the way down at idle.
Basically if the plates are set wrong the top two cylinders can be trying to idle at a different speed than the midlle two and so on, they have to be all exacty the same for the motor to run right. After you get them adjusted open the throttle all the way up and make sure they are all in the same position at WOT. This is one of the most overlooked steps in two stroke carb overhaul, I bet 60-75% of the motors on the water today are wrong.

[trollercoaster]

Thanks guys for the tips. I'll check the carbs but I had felt the mechanic would have checked/adjusted the sync when he rebuilt them. As to the oil inj, it had been disconnected before I bought the motor. I've changed several sets of plugs, and tried different brands (NGK, Autolite, Champion). I've also bought two more switchboxes and tried those.

My plan is to check the fire at the problem speed, under power with these "spark testers" I bouht at H Freight. These are visual indicators of the charge to the plug. I've already tried these at idle with the muffs on and all cylinders looked the same. I guess most of you know that under load things can look different. Hopefully I can narrow down the problem to one or two particular cylinders. I really think it's electrical. It idles OK (as smooth as a typical 2 stroke :-)) and it now seems to run fine at mid and top end but I'm thinking it could also be one carb or one pair of carbs or one of the reeds. Maybe?