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4.3 Mercruiser - randomly dies

R

RBN_TUL

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Need Help Diagnosing Stalling Issue – Tahoe Q5 with MerCruiser 4.3


I have a Tahoe Q5 with a MerCruiser 4.3L engine, and I’ve been fighting an intermittent stalling problem for over a year. I’ve had the boat at three different mechanics, and nobody has been able to permanently fix it.

  • Boat starts and runs normal most of the time.
  • Sometimes, not always, , the engine will randomly shut off after driving for 20 minutes to 1 hr.
  • After it dies, it will always restart immediately.
  • Once restarted, it will run for about 5-10 seconds and then die again.
  • Sometimes, after restarting dozens of times it will run normal again.
  • Some days, it will not have this issue at all.
  • The problem is intermittent and does not seem to happen under a specific set of conditions or after a specific amount of time.
  • I have taken it to three different mechanics that cannot figure it out.
  • New fuel pump install installed.
  • No ethanol in the fuel and fuel stabilizer used.
Video
Picture

Any suggestions or recommendations are greatly appreciated.
 
Loosen the fuel filler cap- if it starts and remains running, it could be caused by the vent being clogged.

Don't start an engine dozens of times, especially in a short time- you'll kill your starter.

How long did those mechanics run it?
 
jimn said:
Loosen the fuel filler cap- if it starts and remains running, it could be caused by the vent being clogged.

Don't start an engine dozens of times, especially in a short time- you'll kill your starter.

How long did those mechanics run it?
Click to expand...
They all took it out on the lake “for hours” and could not get it to replicate.
 
Can we see a steady picture of your 2 gauges?
The main wiring harness cannon plug with the zip tie sort of doesn't appear to be fully plugged in. with just the key on, engine doesn't have to be running wiggle and push in the wire harness and see if the gauges power on and off looking for a bad connection.

Your RPM gauge kind of looks like it surges as it's dying out... Coud be a failing tachometer gauge causing an issue...might try running with the gray wire disconnected at the back of the gauge to see if it helps any...Also look really close for spark leak at the high-tension coil wire to the distributor cap.

May also have an internal issue with the oil pressure switch that is shutting down the fuel pump 12-volt power before the engine dies out.
Item number 10, https://www.marineengine.com/parts/mercury_marine_parts/sn/1A080381/4211025US/13798_40

 
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