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2002 60hp4 stroke EFI continuous alarm

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bajabass

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I am getting a continuous alarm anytime I run above about 4000- 4500rpm. There are 5 reasons listed in the owners manual for this.<br> <br>1. Overheating- There is a new impellar and thermostat installed!! Idle a couple 2 or 3 minutes, water is warming up. No water intake blockage. No water in oil. Power level would be limited, but it will rev fine!<br><br>2. Low Oil Pressure- New oil and filter, level good, engine sounds fine! Power would be limited to 2000rpm, it is not.<br><br>3. Engine Overspeed- Only codes are 2 overspeed codes, I know when both occurred, none lately. Power would limit to acceptable rpm for motor. Alarm sounds at way under 6000rpm redline.<br> <br>4. Low or High Battery Voltage- New battery and spotlessly cleaned connections. Charging at 13-14 volts.<br><br>5. Coolant Temperature Sensor Failure- Limits power to 50%.<br><br>After alarm sounds, I back off to below 2000rpm, alarm stops. I can then run 3000-3400rpm, no problem, approach 4000rpm, alarm goes on again.<br>The engine now has just under 600 hours on it. The thermostat was very crusty when replaced last week. The impellar looked good, but I replaced it anyway. <br>The local Merc guy here in La Paz says to replace the prop with a "bigger" unit, limiting rpm, but this prop has worked fine for 9 years. I am leaning towards a new Coolant Sensor, only because of how corroded the thermostat was. Any help would be GREAT!!! Again, the only trouble codes on the scanner are from 2 times I KNOW I went beyond the 6000rpm redline, momentarialy.
 
The thermostat was very crusty when replaced last week.
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What do you think the internal water jacket looks like? The water temp. probe will look the same. If the probe change does not stop the alarm you may need to demineralize the water jacket w/a vinegar bath.
 
OK, update. Internal water jackets and sensor look good. Very clean in there! Waited 2 weeks to get a 13 pitch prop down here to southern Baja. Boat planes much faster, and cruises about 22 MPH at 4,000 RPM, down from 4,800 with the old 11 pitch prop. Problem is now intermittent. A week ago I made a 40 mile run, never exceeding about 4600 RPM, all good. Went fishing yesterday, cracked it up to 4,000 rpm, and after 10 minutes, ALARM!!! Backed off to idle, and as long as I stayed about 3000 rpm, good. 3500 rpm and up, alarm again. Since my last post, I've changed the oil and filter, lower unit lube, fuel filters and water separator filter just for maintainence. Tried a known good coolant sensor on both tests as well. Any clues guys??? Is there a high RPM poppet valve??? Where is it, how do you check it???? Any help or ideas would be great!!
 
My two cents. The alarm will also sound when there is an amperage over draw. Check your fuel line from the tank to the engine. If the internal liner has come loose from the exterior fuel line case it will cause a restriction and the electric fuel pump will be over loaded and turn on the alarm.

Remove the fuel line and replace it and cut the old one open to see if it is collapsed.
 
All the fuel lines were replaced last December by the Mercury dealer in California, before I hauled it down here to La Paz. There was deterioration going on internally that he spotted in the filters. My fishfinder has a voltmeter built in, and it charges anywhere between 13.5v-13.9v, motor running. I will check the lines again for sure! Anything is posssible I guess. Frustrating fact, the engine runs great until the alarm sounds. Smooth, not overheating, great mileage, ect.
 
Borrow a clamp-on style amperage meter and slip it around the fuel pump's 12 vdc line to get an amp draw reading when the pump is running. I don't know what the amps should be.
 
what you need to do here is unplug and wiggle every wire in the motor to find any loose connections and check all the ring terminal grounds.

You are damn sure your not overheating the motor, right?
 
Water stream is warm, but not scalding, I can touch the cylinder head no problem. I'll try and find an ampmeter to borrow. I'll start the tap and wiggle test next time out. Are oil pressure sending units a known problem for Merc 4 strokes???
 
Thanks for the info guys! The owners manual states battery voltage too high or low, not amperage, would cause the continuous alarm to sound. I will check draw with the engine on the hose, but might be a little hard to do on the water at the engine speeds I am having the issue at. The real odd thing is the scanner shows only 2 overev events in it's history. No other issues in the memory, nada! Any guesses as to the reason for that?
 
OK, update. Finally ran the motor on the water, scanner hooked up. After about 5 minutes at 4000-4200rpm, the alarm sounded. Overspeed code set. RPMs verified on tach by scanner. Never even got close to 5000rpm. Mechanic here in Mexico says it is the ECU/computer malfunctioning, no other plausible culprit. Next test is a known good ECU. Any feedback???
 
Check the crank sensor wiring and all the grounds carefully. I have seen I/O motors do this and the scanners sometimes goes to 35K RPM.
 
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