2001 MerCruiser 496 mag HO.
08-15-2025 | 10:20 AM
#1
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From: Sanford Florida
2001 MerCruiser 496 mag HO.
2001 MerCruiser 496 mag HO
Experiencing issues with engine no start. 2001 MerCruiser mag HO completely stock except for exhaust manifolds
Background is took the boat out and went to leave and was unable to start the engine. Engine turns over, however, have a solid constant alarm and would appear to be a delay in the fuel pumps, engaging.
Upon getting the boat home, determined there was no fuel pressure on the rail. Inspected and replaced the fuel pick up in tank replaced the booster fuel pump, water separator, and fuel filter and primed. Also checked the three fuses on the wiring harness by motor and exchanged the fuel relay. Checked the main harness from the helm to the back of the motor very clean.
Also, this boat is extremely clean with the engine compartment, immaculate no signs of rust or corrosion, particularly in the wires, etc.
Current situation is when the ignition is turned on a constant alarm sounds they fuel pumps are delayed, but then engage and run continuously with no pressure at the rail . There is also a momentary less than a second loss of power about every minute and a half or so, which is also constantly happening.
Upon connecting the tech mate pro the tech mate is unable to find the ECM. And during the momentary power loss, the technique pro restarts each time.
If you have any questions that I can answer happy to do so and appreciate any help in advance. Obviously looking for directions since I couldn’t get codes from the ECM.
Experiencing issues with engine no start. 2001 MerCruiser mag HO completely stock except for exhaust manifolds
Background is took the boat out and went to leave and was unable to start the engine. Engine turns over, however, have a solid constant alarm and would appear to be a delay in the fuel pumps, engaging.
Upon getting the boat home, determined there was no fuel pressure on the rail. Inspected and replaced the fuel pick up in tank replaced the booster fuel pump, water separator, and fuel filter and primed. Also checked the three fuses on the wiring harness by motor and exchanged the fuel relay. Checked the main harness from the helm to the back of the motor very clean.
Also, this boat is extremely clean with the engine compartment, immaculate no signs of rust or corrosion, particularly in the wires, etc.
Current situation is when the ignition is turned on a constant alarm sounds they fuel pumps are delayed, but then engage and run continuously with no pressure at the rail . There is also a momentary less than a second loss of power about every minute and a half or so, which is also constantly happening.
Upon connecting the tech mate pro the tech mate is unable to find the ECM. And during the momentary power loss, the technique pro restarts each time.
If you have any questions that I can answer happy to do so and appreciate any help in advance. Obviously looking for directions since I couldn’t get codes from the ECM.
Last edited by Mjongsma; 08-15-2025 at 10:44 AM.
08-15-2025 | 11:47 AM
#2
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Joined: Dec 2016
Posts: 582
Likes: 363
From: Portland OR
That's a tough one. These Motorola 555 PCMs are known for issues especially since these engines are getting some age on them. You may need to get your PCM checked out. There's a few guys in the country that can repair them still.
