Possible water pressure fault(MY2009 350MAG MPI)

silver_power · Jul 2, 2012

Hello, i repowered my boat in 2009 with a totally new 350Mag MPI.
Well, everything till now is just perfect with the new engine and i had no problem till yesterday. Everything run ok , cruising with 32Mph but as i scrolled the smartcraft screens, i saw that the water pressure was VERY LOW at about 0,00-0,02 bar=0 - 0,3psi! The engine temp was totaly correct 71oC steady. I tried to 45mph and the water pressure raised to 0,10bar=1,45psi. Then back again to 30mph and the water pressure falled again to 0 - 0,01bar while the engine temp was steady at 71oC. The engine has 130hours,...and i think that as the temperature was ok, then the impeller works fine and so the water pressure sensor might be faulty. What do you think?The smartcraft even when the reading was 0,00 bar, did not make a bip or any alarm. I thing that the water pressure sensor is mounted on the power steering cooler. Am i correct? Can you please give me the part number and how can i change it? I am asking just because the boat is in the sea and i want to be sure about the tools i will need.
Thank you very much,...

Bondo · Jul 2, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

silver_power said:
Hello, i repowered my boat in 2009 with a totally new 350Mag MPI.
Well, everything till now is just perfect with the new engine and i had no problem till yesterday. Everything run ok , cruising with 32Mph but as i scrolled the smartcraft screens, i saw that the water pressure was VERY LOW at about 0,00-0,02 bar=0 - 0,3psi! The engine temp was totaly correct 71oC steady. I tried to 45mph and the water pressure raised to 0,10bar=1,45psi. Then back again to 30mph and the water pressure falled again to 0 - 0,01bar while the engine temp was steady at 71oC. The engine has 130hours,...and i think that as the temperature was ok, then the impeller works fine and so the water pressure sensor might be faulty. What do you think?The smartcraft even when the reading was 0,00 bar, did not make a bip or any alarm. I thing that the water pressure sensor is mounted on the power steering cooler. Am i correct? Can you please give me the part number and how can i change it? I am asking just because the boat is in the sea and i want to be sure about the tools i will need.
Thank you very much,...

Ayuh,.... If the impeller hasn't been changed since the swap,.... I'd start there....

silver_power · Jul 2, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

No, the impeller has not been changed since the engine swap. I put new impeller kit when i swaped the engine. Another test i made for the impeller condition was the following. The operation temp of the engine was 71oC, i turned off the engine and looking the digital reading of the temp from the smartcraft system.After about 2minutes, the temp raised to the 77oC. I then started the engine at idle and the temp falled immediately to 66oC, while the water pressure reading was 0.00-0.01bar!. I think that this is a good test for the impeller condition. If the impeller was not working good, the engine temp would not falled immediately under water condition 0bar! What do you think about that?

Bondo · Jul 2, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

silver_power said:
No, the impeller has not been changed since the engine swap. I put new impeller kit when i swaped the engine. Another test i made for the impeller condition was the following. The operation temp of the engine was 71oC, i turned off the engine and looking the digital reading of the temp from the smartcraft system.After about 2minutes, the temp raised to the 77oC. I then started the engine at idle and the temp falled immediately to 66oC, while the water pressure reading was 0.00-0.01bar!. I think that this is a good test for the impeller condition. If the impeller was not working good, the engine temp would not falled immediately under water condition 0bar! What do you think about that?

Ayuh,... I think impellers are only good for a year, maybe 2 Tops, 'n yer's is way past it's useful life...

In ANY overheat situation, the Impeller is the 1st thing to change....

silver_power · Jul 2, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

You have absolutely right, but i have not overheat problems. I tried the boat with 30mph and 60mph as well in W.O.T. The boat was running awesome and the engine temp was 71-72oC. While running at 30mph, the water pressure reading was 0-0,01bar and in W.O.T the reading 0,12bar, but i notice again with no overheating problems. I suppose that if the impeller was not good, then definately the engine temp would be raised in higher temperature immediately in W.O.T.Am i correct? I am trying to find out what is going wrong thinking the facts and the test i made because changing a sensor is absolutely easier that pull out the drive as the boat is into the sea.....

silver_power · Jul 3, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

What do you believe i should test firstly?......You are suggesting me to take the boat out of the sea to check impeller?...or preferably to check the water pressure sensor? And how can i test it???

Bondo · Jul 3, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

silver_power said:
What do you believe i should test firstly?......You are suggesting me to take the boat out of the sea to check impeller?...or preferably to check the water pressure sensor? And how can i test it???

Ayuh,.... What drive are We talkin' 'bout,..??

If the impeller is old, 'n stiff, it don't pump water like a New 1....
If that's the case, the water Pressure is also gonna be Low...

You can do whatever ya want,...
But,...
As I said above, the 1st thing to do, when fixin' a boat's cooling system, is to Change the Impeller...
'n yer's is Waayyy past it's Expected service life...

silver_power · Jul 3, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

It is an Alpha one GenII drive.
All i want to avoid is to take the boat out of the water, because my trailer is about 100miles away from the boat.......
The impeller is 2years old,...with 130hrs,.....
anyway,....i will check next weekend the pressure again and i will be really careful with the temperature.
But i must tell you that 2weeks ago, before i put the boat into the water, i started on the trailer at idle with a garder hose to suck water from. The smartcraft screen then showed 0,10bar at idle and the exhausts was throwing water normally as always,.....After that the boat run only about 2hours with no overheating problems even at W.O.T!!

silver_power · Jul 5, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

Can anyone please give the part number of the water pressure sensor for my engine? It is a 350Mag MPI MY2009.
Thank you very much.

Don S · Jul 5, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

Go to this link http://www.mercurymarine.com/parts-and-accessories/parts-catalog/#epc::model_find then type in your serial number.

silver_power · Jul 5, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

I cannot find it.........
I know that it is mounted on the power steering cooler.
My engine serial is 444126LUU.
Please can you help me?

Don S · Jul 5, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

silver_power said:
I cannot find it.........
I know that it is mounted on the power steering cooler.
My engine serial is 444126LUU.
Please can you help me?

That isn't a serial number, not sure what it is. Your engine should have numbers that start with 1A and 6 numbers following. ie. 1A123456
I could probably look it up, but I would need the serial number. NOTHING is listed by year for Mercruiser after 98, only by SN and range.

silver_power · Jul 5, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

Ok , i will check it this weekend and i will tell you.
What do you really think about my problem......did you please read what happens with my water pressure reading while absolutely there are no overheating problems?

Scott Danforth · Jul 5, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

could have a bad water pressure sensor, however since you have 2 years on the impeller, its due to change. I would start there.

silver_power · Jul 6, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

To my old engine 5,7LX 4bbl, i used to change impeller every 5-6 years and i never had overheating problems. The impeller after 5 years of operation was in very good condition comparing with a new....Probably, as i NEVER operate the engine to less than 1meter and very close to coast, it never sucked sand etc. This may protect the impeller and keep it in good condition. So that is why i am surprized to have problems with the impeller after 2years. Besides ig the reading is 0,00bar, then the impeller does not suck any water and so i would have definately overheating problems. What do you thing?
Thank you very much.

silver_power · Jul 6, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

....

achris · Jul 6, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

I think the general mentality of changing impeller every 2 years is from the old high pressure, low volume impeller days... They finished in 1991. The new 'floppy vane' impellers last considerably longer, and will withstand far more abuse than the old 'short vane' impellers... I check mine every 5 years, with a view to changing it every second check (10 year service life). I have several other customers with the same drive (Alpha One Gen II) whom I have the same policy with, and never had a problem....

From your description of what you've checked and how you've gone about it, I'd say that you're right, it's just the sensor... The part number is 8M6000623. Looks like the price is about $120. And it's not uncommon for them to fail. But I'd do some basic checked before I shell out that kind of coin...

1/ Check the wires to the sensor.
2/ Carefully stick a probe in each connector wire and check you have +12 and a good ground. The wires are blk/pink is +12v; grey is ground; dk blu/white is sensor output.

The tools needed to change it are just a spanner and some thread tape... (yes, you can use thread tape as the sensor connector carries ground to the sensor, it's not though the body of the sensor.)

Good luck.

Chris........

silver_power · Jul 6, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

Exactly,...i check the impeller every 5 years, it is like new and i change it just because everyone tells that we should change it every 2years.....Anyway,..about my problem i think exactly the same and i will do these test with the cables. I do not know why the smartcraft system does not make a bip or an alarm with an error message. I find out the 0,00bar reading completely by luck!!Shouldn;t i have any kind of alarm?

achris · Jul 6, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

You should have heard two warninbg beeps per minute. I an not familiar with Smartcraft, but it may disable some of the warnings. I woul unplug the sensor and see if you get any beeps...

silver_power · Jul 9, 2012

Re: Possible water pressure fault(MY2009 350MAG MPI)

Well, it is definately the water pressure sensor issue.....
I started the engine and the water pressure reading 2,45bar @idle.....and after about 5seconds it went to 0,01bar......but no beep....
I did not had the time to check anything with the cables, but i will fix it or change the sensor....
Thank you very very much.

Possible water pressure fault(MY2009 350MAG MPI)

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