unusual motor performance

carazola

Recruit
Joined
Sep 29, 2018
Messages
1
hi mates, I am new to this forum, I am writing on behalf of my longtime mechanic who does not do computers very well.
I have a 2002 mercury saltwater 150 outboard with low hours, which you could probably eat off of, for reals.
The most recent repair required replacing the stator. My mechanic also did a tune up decarbed the carbs and installed new plugs, but I think the stator was the major culprit of my last engine trouble. first question, can you get a partially working stator from the manufacturer.
The current motor trouble is that the motor runs smooth from idle to 2100 rpm, then when applying throttle, it develops a coughing or stuttering. This stuttering or missing occurs up to about 3700 rpms, but from there to 5100 rpms or the top end it seems to run and sound fine. The mechanic went for a ride with me to ascertain if I was correct or not in thinking we still had an issue, he agreed, something not right here.
He had it another full day without coming up with anything else. my first thought was that the stator he just installed was defective from the factory, not sure if that is possibe. He checked the ignition and coils, but apparently did not think that was an issue. Does anyone have any ideas about what could be possibly causing this missing or coughing between low and high rpms? Thanks in advance for any and all comments suggestions.
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
8,293
Yes it can be defective. Did you test it CDI Electronics has the testing guide.
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
14,118
Since you probably can get 3700 rpm with full timing advance, before the carbs really start to open, I would be checking the sync between the carbs and spark, and a thorough cleaning of the carbs. You said the mechanic "decarbed the carbs"... What does that mean? When he was messing with the carbs, did he buy overhaul kits for them, and did he remove all the welsh type plugs to clean the off idle ports on the carb throat? And did he perform a link-n-sync?
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,862
If what you typed is accurate account of actions taken by the mechanic, he should diagnose before tinkering and replacing parts, AND you should find a new mechanic.

Testing comes first.

What exactly is “decarbing the carbs” ?
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,937
Post a serial number...That should be a CDM ignition system and could have a control module mounted on top of engine. That could be the problem not stator
 
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