Mercruiser 5.0L MPI with Alpha Outdrive - Cooling Water Pressure Issue

[jberntsen]

I have a 2006 Sea Ray 225 Weekender with a Mercruiser 5.0L MPI engine. Had an alarm sound on Tuesday with no particular warning message on the SmartCraft display:facepalm:. Looking over operational parameters, I noticed that the water pressure was in the 28 to 32 psi range which looked to be on the high end. Engine temp was between 148 and 160 and operation was smooth. Alarm cleared when engine was shut off. Ran again for 30 minutes with no issue. Alarm sounded again when we returned to idle nearing the dock. Initial alarm occurred while in idle.

It does not appear to be an obstruction on the cooling water side. Could it be a bad pressure sensor and sending unit? Anyone know where the sensor is located? How to test? Normal Operating Range? My thought is to remove and replace with an accurate manual gauge to test pressure then replace, clean, or troubleshoot the sensor.

Thoughts or ideas? Thanks in advance.

 

[achris]

Re: Mercruiser 5.0L MPI with Alpha Outdrive - Cooling Water Pressure Issue

Water pressure sensor is located in the power steering oil cooler, on the under side, port side end... Here's the bad news... The cooler's at the back of the engine... Normal water pressure should be in the range 1-5 psi at idle and 7-17psi at WOT....

The sensor has 3 wires on it, one to ground (blk/pink), one to 12 volts (grey), and the signal wire (Dk blu/wht). It's a simple voltage divider, if the reading is going high, suspect the ground connection (either at the sensor or in the harness) or a faulty sensor. Part number for the sensor is -881879010, and will cost you (YIKE!!!) $102.... (Hope mine never fails!)

 

[jberntsen]

Re: Mercruiser 5.0L MPI with Alpha Outdrive - Cooling Water Pressure Issue

Thanks for the reply, Achris. I will dig in to it later this morning to see if I can find it. I'll post results/additional questions as I go.

Thanks again!!

 

[jberntsen]

Re: Mercruiser 5.0L MPI with Alpha Outdrive - Cooling Water Pressure Issue

Well, the SAGA continues.:facepalm: The water pressure sensor is replaced. Took it out for a ride with the family over Christmas break. Ran for 30 minutes just fine. Then the alarm went off...turns out the local dealer sold me an Oil Pressure Sending Switch; 0-100 psi. I needed the Water Pressure Sending Switch; 0-50 psi (FYI - they look identical and are off by one single part number.....) I swapped the wrong part for the right one and the wonderfuly nondescript "Check Engine" warning is now sounding. Is there a "reset" procedure to clear the alarm condition? Other than the generic smartcraft +/- hold for 10-sec and watch it go boom?

I just don't want to tow it to the dealer and waste a day of my time taking it over and back when it is something I can take care of.

 

[Pete104]

Re: Mercruiser 5.0L MPI with Alpha Outdrive - Cooling Water Pressure Issue

Mercury had an issue with those sensors. Anything manufactured prior to May 2008, "may have a machining error that allows an internal o-ring to by-pass water into the sensor."
Also, that p/s cooler is bear to ground. Double check that.

 

[dubs283]

Re: Mercruiser 5.0L MPI with Alpha Outdrive - Cooling Water Pressure Issue

throw parts at it until you resolve the problem or run out of money - thats your approach

bite the bullet, have your local dealer take the boat for a day, check the fault codes and replace the faulty component and have you continue boating - thats the logical approach

everyone can guess at the issue here but noone will know the correct problem until the faults are checked