2.5 200 problem, help please!

[sean1982]

hi, im still having problems with my merc.
its really down on power bogs and pops all the way up to 6k
so far i have put a new stator, trigger, coils, leads, plugs, switch boxes, checked carbs, new base gaskets and crank seals. comp is 115psi on all.
checked the plugs and number one was dry and all the rest looked wet and black but cleaned up like new.
gonna check reeds and bleed check valves too.
any ideas would be welcome,
cheers

[Eagle One]

Try this: IF it has any kind of idle stabilizer box, advance module or if you are still running the oil injection. Try disconnecting all the boxes other than the basic ignition components. Run it and see if that helps. Next,Get a dial indicator and find top dead center for every cylinder and mark TDC and 22 degrees BTDC on your flywheel and check the timing fior every cylinder. IF you have not checked the timing it might very well be the problem. IF it has one of the large cast flywheels , check the magnets. They are glued in and bad to come loose. Maybe this will help but without more info it's just a guess.

[sean1982]

all idle stabiliser and oil injection was removed and it was timed at 23 degrees, and all cylinders were checked, its 16amp electrics and the light ally flywheel.
went down today and rechecked the carbs, all good and sealing, exhaust divider gasket was good, as was the head gaskets, these will be replaced now. reeds checked out good, and the bleed check valves all work as they should. im really stumped now????

[t.martin]

Check all of your grounds on the motor and ignition swith. Very common. especially if it has been tore down recently

[sean1982]

all grounds on the motor are good, how does the ignition switch make it bog and struggle to get the revs up? but i will try taking the black and yellow wires off the switch boxes though.

[t.martin]

A buddy of mines boat kept falling on its face at like 4800 then come alive again. The kill circuit in the ignition switch was acting up.

[sean1982]

its worth a try! im clutching at straws now!

[t.martin]

Did you remember to put the bias circuit (black and white jumber) between the switchboxes?

[sean1982]

yeah, i have checked everything 2-3 times now, making sure its all right. this seems to have happend after i fitted a brand new stator removed the idle box and timed at 23, and put all new 3/8 fuel hose and fitted a new holley red top and new reg set at 4.5 psi. there was a facet red top and reg set at 4.5 psi on before.
tested pressure on a gauge and its all correct.
seems to have fuel soaked on the outside of the carbs too, but cant work out where its coming from as all the carbs are sealing correctly

[t.martin]

If it is popping it is more than likely a timing/ignition problem. The dry plug has me concerned though. Hopefully some of the more experienced guys will reply soon

[M. HARDEE]

you stated it happen when u change to new stator -----BAD STATOR ?????????or check wire order on boxes or broken wire in that area disturbed when changing stator . UN HOOK TAC have seen tac case irratic short in ignition ------ if fuel soak at top cap and running down on carbs ==could be blown top crank seal .

[sean1982]

crank seals have been changed, and could a brand new oem stator be bad?

[sean1982]

could it be my idle pickup timing to retarded, as when i removed the idle stabilizer we had to retard the timing quite abit to get it to idle low?

[gmacrae]

Did you remember to put the bias circuit (black and white jumber) between the switchboxes?

This is what caused my problems after removing the modules

[gmacrae]

could it be my idle pickup timing to retarded, as when i removed the idle stabilizer we had to retard the timing quite abit to get it to idle low?

how low is the timing? Some around here like the idea of using idle timing to set idle speed - i've found too much retard makes it lazy outta the hole, so set about 2-4 degrees atdc, then set idle speed with throttles - just my (limited) experience.

[sean1982]

idle is about 10-12 atdc, as after i removed the stabilizer it would idle at around 2000rpm so had to turn it down.

[t.martin]

I think you need to pull the flywheel and check the trigger and stator wires. If they are not seated perfectly the wires can get rubbed by the flywheel and cause some real weird issues.

[sean1982]

Trigger and stator wires are fine had the flywheel off loads and checked everything, no issues wire anything like that. I have had this problem ever since the timing was played with, but the guy who done it swears its fine. Im not so sure now.

[t.martin]

I am just pointing out problems that I have ran into in the past. If you are doing the work yourself give me a call att 814-977-6147 (Trent) and I will explain some things you can try. If you are having someone else work on it then you need to take it somewhere else. It won't last long if it is popping at 6,000 rpms

[gmacrae]

idle is about 10-12 atdc, as after i removed the stabilizer it would idle at around 2000rpm so had to turn it down.

That's some lazy timing. Try bringing the timing up closer to 0 and setting idle with the butterflies, i know it doesn't really sound like the cause of your exact problem but it definitely wont hurt.

[Go Time]

With a 2.5 carb motor and no advance module, it should idle nicely between 2-8 degrees with no butterfly opening. (in gear, in water ~700RPM) unless you've worked the ports. Check your main jets to make sure none are loose. Are you sure you needle and seat are working @ 4.5PSI fuel pressure? Is your enrichment valve leaking by?
Mark

[sean1982]

checked the enrichment, needle seats are sealing good. i just cant understand that this has happend since the idle stabilizer was removed and the timing was set. also as soon as the stabilizer was removed the idle went high. but could that cause me problems?

[Go Time]

Did you idex the timing reference indicator before adjusting the timing to ensure it was right? I have loads of carb 2.5L 200's with no idle stabl module idling fine at 6-8 degrees ATDC w/ butterflies closed and lanch great. Also, make sure your throttle linkage is properly set up prior to timing the engine.

The fuel outside the carbs worries me, do you have a vacuum leak? bad carb gasket, split centermain bleed line or emrichment line. Do you use an air box and if so, is fuel pooling there?

[sean1982]

yeah he got tdc on all cylinders. so it cant be timing then?

[sschefer]

could it be my idle pickup timing to retarded, as when i removed the idle stabilizer we had to retard the timing quite abit to get it to idle low?

Sounds like your middle carb set is opening too early. Re-synch the carbs and make sure all the butterflys on all the carbs completely close. Make sure you tighten the screws back up starting with the top and holding down on the linkage but not with a lot of pressure. When you tighten the screw on the middle carbs make sure they don't kick open on you.

That will cause the wet carb syndrome also. Been there and done that my friend. It's really easy to do and you end up looking at everything else on the motor because you know for sure you did it right. It's just another one of those Merc gotcha's.

Best of luck.

Oh, if you get it right, you'll need to adjust your initial timing back where it should be.

[sean1982]

ok cheers i will try that, is there any set way to link and sync? is it just the carbs i need to do?

[sschefer]

The 2.5's are really easy but you need to follow the procedures in the Service Manual if it's your first time. I don't have it in front of me right now, I'm at work playing hookie on S&F...LOL.. Maybe someone else can chime in here.

[sean1982]

Ok cheers, if anyone can tell me how to do a formal link and sync, plus timing correctly that would be great thanks!

[j_martin]

You need to get the service manual and do the timing and linkage adjustments (link-n-sync) just to establish a base line for troubleshooting. With the timing you're describing, either the timing pointer is off, thus all the timing is a crap shoot, or you have a serious air leak or carb issue. Any of this can make it throw parts at you, so it's critical it gets done right, and soon.

And yes, you can get a bad part out of a new box, and you can wreck a good part installing it.

hope it helps
John

[j_martin]

infamous S&F double whammy