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Merccrusier Fault code 37 Blk Pres Low

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fivestand

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"I have MCM 350 MAG MPI, Engin

"I have MCM 350 MAG MPI, Engine Serial number - OW327362,
Drive - OW271996. I get the two-beep guardian code when the engine is running and with just the key on. The computer fault code is 37 Blk Pres Low.

I had some slight blockage in the stern drive intake and cleaned that out. I still have the same error. My question is:

How do I check the sensor?

If the sensor is bad can I replace the sensor while the boat is in the water? (The boat is slipped) Thanks"
 
"I guess you have a smartcraft

"I guess you have a smartcraft display, and that is where your seeing the fault code. According to the smartcraft display, what is the seapump pressure when the engine is off, at idle, and at cruise speed? This will help determine if the seapump pressure is actually low, or if it's the sensor.

The sensor is mounted on the seapump on earlier models, and on the power steering cooler on later models, but either way it's not a big deal to replace it. The boat can be in the water."
 
"Dave,
I do not have the smar

"Dave,
I do not have the smartcraft. I bought the Mercruiser scan tool, it reads 0 at idle. I was afraid to take out and run it. It is a 2005 bayliner. Should I take it and run it with the scan tool hooked up?"
 
"You should be able to check i

"You should be able to check it without actually taking the boat out of the slip. It should be 1 to 3 PSI at idle and about 10 PSI at 2500 RPM. You basically want to see if it's acting logically, meaning the seapump pressure is 0 when the engine is off and then with the engine on, it's low at idle, and increases with engine speed. If it increases with engine speed but has low pressure across the RPM range, you may have a weak pump.

If it doesn't act logically, like it's 0 at idle and stays at 0 regardless of engine speed, and the engine does not overheat almost immediatly, then it's probably the sensor. If it's 40 PSi with the engine off it's the sensor."
 
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