Mercury 225 Offshore- LOSING MY MIND PLEASE HELP

Fletcha221

Recruit
Joined
Nov 20, 2020
Messages
4
Started this under another thread where I was certain I had a bad stator, unfortunately, that's not the issue. My mechanic seems to think the flywheel has gone bad (apparently magnets are glued into the flywheel? He seems to think one magnet came loose? If you read below, I THINK its the last logical thing that could be causing the issue.

Has anyone experienced this?

When we broke down, running at 4k rpm, engine just stopped. There was no poor running, just stopped like someone turned the key to "off".

When starting from "cold" the motor comes to life for a split second (sometimes) and hunts around and stalls. It wont stay running. All cylinders have spark (but I'm guessing the timing is off or the spark is weak), all cylinders have equal PSI. There is fuel, and all floats in the carbs are working correctly.

The house systems on the boat are 100 percent mutually exclusive from the engine (Besides the 12v key wire powering the Gauges , I have completely removed the neutral safety switch, and replaced the key switch.

The batteries are good, all grounds and hot leads are clean and secure. (cleaned and retightened). The ground straps for the ECU are clean and tight as well. I pulled a gallon of fuel, there is no water in the fuel. All coils are tested. Carbs have been rebuilt, and did a link and sync on the carbs and I have replaced the following:

1. Crank position sensor (correctly gapped to factory spec)
2. NOS matching CDM (ECU)
3. Tested used stator
4. Mercury Key switch (Ignition)
5. Starter Solenoid
6. Starter
7. Plugs
8. Fuel Pump

It has fuel, spark, and compression......it just wont run. Just sputters, hunts around in RPM then dies, within 5-10 seconds.

I seriously can't think of anything else that could be wrong with the motor, besides it being a Mercury:)

HELP!!!!!
 

Dukedog

Captain
Joined
Oct 6, 2009
Messages
3,420
if it lost a magnet (they are glued) there would be no doubt... have you tried squirting (pre mix) straight in to tha carbs when it starts ta "hunt" or shut down?
 

Faztbullet

Supreme Mariner
Joined
Mar 2, 2008
Messages
15,904
Magnet aint the problem...... what the # on ECU and have you checked TPS on carb?
 

coves

Seaman Apprentice
Joined
Sep 26, 2004
Messages
41
Started this under another thread where I was certain I had a bad stator, unfortunately, that's not the issue. My mechanic seems to think the flywheel has gone bad (apparently magnets are glued into the flywheel? He seems to think one magnet came loose? If you read below, I THINK its the last logical thing that could be causing the issue.

Has anyone experienced this?

When we broke down, running at 4k rpm, engine just stopped. There was no poor running, just stopped like someone turned the key to "off".

When starting from "cold" the motor comes to life for a split second (sometimes) and hunts around and stalls. It wont stay running. All cylinders have spark (but I'm guessing the timing is off or the spark is weak), all cylinders have equal PSI. There is fuel, and all floats in the carbs are working correctly.

The house systems on the boat are 100 percent mutually exclusive from the engine (Besides the 12v key wire powering the Gauges , I have completely removed the neutral safety switch, and replaced the key switch.

The batteries are good, all grounds and hot leads are clean and secure. (cleaned and retightened). The ground straps for the ECU are clean and tight as well. I pulled a gallon of fuel, there is no water in the fuel. All coils are tested. Carbs have been rebuilt, and did a link and sync on the carbs and I have replaced the following:

1. Crank position sensor (correctly gapped to factory spec)
2. NOS matching CDM (ECU)
3. Tested used stator
4. Mercury Key switch (Ignition)
5. Starter Solenoid
6. Starter
7. Plugs
8. Fuel Pump

It has fuel, spark, and compression......it just wont run. Just sputters, hunts around in RPM then dies, within 5-10 seconds.

I seriously can't think of anything else that could be wrong with the motor, besides it being a Mercury:)

HELP!!!!!
Have you verified that all fuel lines are in perfect health? Went down the rabbit hole with a similar issue (96 225 efi mariner). Turned out the inner linning of the fuel line had disintegrated and pretty much cut off fuel supply and this being fuel injection, clogged that up as well. This engine was stated to run on 10% ethanol. Not any more!
 
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