200 HP merc 1993

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ct26sutphen

Cadet
Joined
Jul 13, 2008
Messages
6
I started out with a 200 Hp merc that idled rough and sometimes stalled.
I brought it to a mechanic and things have gotten worse.

First they said it was the carbs so they rebuilt them even though they were clean when taken apart.

Then they said it was a stator, I tested it and it came back fine.
Then they cleaned all the connections on wires and spark got better and better but when they fired the engine it went to 2500 RPM and stayed there.

It had run fine after the carbs but still wouldn't idle well.

So now it seems to be stuck at 2500 RPM or higher and has considerable timing issues with jumping all over the place.

They had me go get a new trigger too and that didn't help at all.
can anyone tell me what they have done wrong?

At least I could use the boat before now its useless!
 
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emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 200 HP merc 1993

You say that timing is jumping all over the place? I'd say that's a clue to your problem. If this motor has an idle stabilizer, I'd recommend disconnecting it and throwing it away!

How did you check the stator, with a meter? What were the resistance values?

It still sounds like an issue with the stator but of course it's a lot more difficult to diagnose 'long distance'.

Has anyone inspected the ign coils? Infamous for cracking which can lead to intermittant arcing to ground, causing misfire and other running issues. Each coil should be disconnected and removed from its mount. Inspect all over for cracks, pull back any insulating rubber etc and check behind for cracks too; sometimes they're hidden.

And here's some good basic troubleshooting guide for ADI igns, maybe something in here will help:

http://outboardparts.com/mercury/troubleshooting/troubleshooting10.htm

http://dolphinmarineservice.homestead.com/ign5.html

http://www.boatpartstore.com/mercreadings.asp

Note that most troubleshooting can be done with a V.O.M., by checking resistance values. Where a DVA comes in handy is when you're chasing down pesky problems like yours.

http://www.iboats.com/CDI_511_9773_NL_Without_Leads_DVA_Peak_Voltage_Adapter/dm/view_id.336045

http://www.boatfix.com/bykeywordnew2cdi.asp?textfield=511-9773&texttype=2&submit=Search

Anyway, check that stator real close. If the values are even slightly outside the resistance specs, it's probably bad. If there is any melted "potting material" oozing out of the stator, or any visible burn marks, it's shot.

Hope that helps or at least gets you pointed in the right direction!

And I would seriously think about getting new mechanics, the guys working on your motor obviously don't have a clue or they would have gotten it fixed by now, without all the Easter-Egging of parts!

G'luck & let us know what you find, it'll help others to diagnose/fix similar problems in the future..........ed
 
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ct26sutphen

Cadet
Joined
Jul 13, 2008
Messages
6
Re: 200 HP merc 1993

Thanks for the input.

I will look into all the info you supplied.

My mechanic is a good guy but is a OMC, evenrude mechanic. Its a whole different ball game apparently.

When He checked it the first time he used cranking volts or amps it came back OK but supposed ly now It comes back bad using resistance. That still doesn't explain the higher RPM after putting it back together.

What could cause that.
The Idle stabilizer was diconected and the problem persisted.
could the stator cause that?
He now says the stator and the coil packs are the culprit.
 
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ct26sutphen

Cadet
Joined
Jul 13, 2008
Messages
6
Re: 200 HP merc 1993

Anyone know how I can do a parts look up by serial number so I can get the right stator?
 
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emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 200 HP merc 1993

Search for CDI parts here:

http://www.boatfix.com/searchcdi.asp

If you have trouble from the Application Chart which one to get, do a search here, based on your Serial #, and it'll tell you what the Mercury part number is for the stator. Then you can cross-over to a CDI part #.

http://www.mercruiserparts.com/SelectModelType3.asp?class_id=2

On the 'coil packs' if the mechanic means the ignition coils, why is he all of a sudden thinking that the coils are bad??

If the coils pass a resistance check and they don't have any cracks/arc marks, there's no good reason to replace them. And if you have a dead coil, you can confirm it's fried by swapping in a known good coil and see what happens.

If the problem follows the coil, it's bad. If not, then you at least know it's not the coil............ed
 
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ct26sutphen

Cadet
Joined
Jul 13, 2008
Messages
6
Re: 200 HP merc 1993

The old mechanic was a evinrude OMC mechanic and this new diagnosis was by a friend of his who is a merc mechanic and did him a favor.

I did not know that the the two were so diferent.
I have the boat home now and I am fixing it myself .

The reason he thought the coils were weak was do to the miss in two cylinders and the weak spark.

They may have tested it though I was not there.

My main concern is the jump in RPM after he cleaned the terminals on the engine Switch boxes, coil plate etc. The engine idled fine at normal RPM, then he cleaned things and put it back together and the RPM is now at 2500 at 0 throttle input.
The rest is fairly simple t me but thats got me puzzled.
 
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