Engine Weirdness

scrat

Petty Officer 2nd Class
Joined
Sep 21, 2007
Messages
106
I posted this in the outboard section too bu thought I'd also give it a go here. I have an mercury optimax 150 on my 2002WA. I can be cruising and everything is running fine at 3500-4000 rpm with no issues. then it just quits with no alarms, no warning, no poor running. happens intermittently. Stops just like the emergency cut off was thrown. starts right back up with out a blink. Tried to find a short that may have caused this in the cut off switch but no joy.. any ideas? Thought I ask opinions before I carried it into the shop.
 

NWFisher

Cadet
Joined
Feb 1, 2008
Messages
15
Re: Engine Weirdness

Hi Scrat,
It sounds like an intermittent electrical problem. The Mercury Service manual says no spark causes include:
1. Bad stop circuit
2. Bad stator
3. Bad Control Module

I suggest starting with a physical inspection:
1. Battery terminals. Disconnect the wires from both terminals, inspect for corrosion, correct any corrosion or poor end connectors found and reconnect.
2. Internal engine fuses. Remove each, inspect and re-install.
3. Internal engine wiring connectors. Look for a correct any corrosion.
3. The wiring harness from the emergency stop switch to and into the engine. Disconnect each connector and check for evidence of corrosion (could be a sneak path to ground) and clean up any corrosion found.

You already checked for shorts but since it's intermittent testing will be difficult. The stop circuit (emergency stop switch) is normally open and shorts to ground when emergency stop is activated. As you probably already do, start the engine on the trailer and while running:
- Wiggle/shake all the wiring harnesses.
- Wiggle the ignition key.
- Ensure the emergency stop switch works

If nothing is found and the problem continues then it's probably a trip to your favorite mechanic or replace the Control Module.
NWFisher
 
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