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I need help please folks. Mercury 4stroke vibrates and stalls at times only

Q

qhn

Regular Contributor
2002 Mercury 60hp 4stroke motor with 209-218psi on all 4 cyl, spark is good, all good as checked, cleaned carburators 3 times, all passages flow good, acceleration plungers are good and front nozzles spray strong, new needle valves and all floats are good and levelled..
New rectifier, new fuel pump, changed out coils...
Motor will starts right up and idles nice, put in gears vibrated a bit, but can troll around all day. As soon as I gradually increased speed, motor virated harder and stalled. Starts right up. If I slammed on throttle to WOT, it took off quickly on plane and ran like a champ. Gradually decreased speed, it would vibrate and stall out (shut off immediately). But if I quickly dropped it down to neutral, it would stay running. So somewhere in the 2000-3000rpm this vibration gets huge and stalls the engine. Other than that it runs ok. I am really stump right now and don't know what to do next. Could it be a stator issue? I pulled the head and check valves and all are good. New head gasket is on the way. Valves open and shut in order 1,3,4,2...no problem. I readjusted some of the valves before reinstall them. But at this moment, I can't afford to go dig around further without having a good direction to go...
Any advice is deeply appreciated.
 
You need to find a local Merc mechanic who can set up this engine for you. They are very sensitive to link and sync adjustments. All adjustments have to be made with the boat in the water.
 
Thank you Chris. So you think it's link and sync issue! I will dig into that. When I first hook up the battery I saw a little spark on the terminal, I thought it was the voltage regulator. But now the short is gone. I more aiming at the carbs or the stator or even the module...was hoping you would tell me to test the stator. Firing order 1,3,4,2. The coils are at 1,4 and 2,3. Does this seem right? Bottom coil is 1,4 and top coil is 2,3. Could it be marked incorrectly?
Again, thank you for the reply.
 
Thanks again. I oredered a used set of carbs and will try out. Really appreciated you. You're the best!
 
If the carbs are off a running motor...why are we synchronizing them? Don't they just need to be cleaned out and put back in. Wow! This carbed motor requires more than I thought. I've been cleaning them carbs of '99 to '05 Merc and have turn them from no starting to starting and running like a champ all these years. Amazing how I realize "the more I learn, the more stupid I feel how I was". Thank you very much. I gotta set up those gauges ASAP.
 
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