Mercruiser 5.0 MPI raw water pump impeller replacement

klopf

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Jul 13, 2016
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Engine: Mercruiser 5.0 MPI year 2010
Sterndrive: Alpha one gen. 2
Gauge: Merc. Monitor
Water inlet: Only from the bottom of the boat through raw water pump. No impeller in the drive
Cooling: Closed cooling

Hi

I need to replace the impeller in water pump. I have throu the hull inlet.
Is it safe to replace it while the boat is in the water?
I guess I have to close the seacock.
When removing the two hoses from the pump house I imagine all raw water will come out into the bilge and I need to empty it with the bilge pump. And if the seacock works, no more water will flow into the boat. Is there any risk that water will flow into the boat from the raw water outlet?
 

Bondo

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Apr 17, 2002
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70,465
Ayuh,.... Welcome Aboard,..... So long as ya close the sea-**** you'll be just fine,.....
 

alldodge

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Is there any risk that water will flow into the boat from the raw water outlet?

No water will enter the boat with the seacock closed, Provided the seacock is not worn out. Close the seacock then remove the hose, if it leaks it will not be that much in most cases, just be ready to put it back on if the water keeps flowing hard. Being a 2010 I don't think there should be any issue
 

Bt Doctur

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Aug 29, 2004
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Put the impeller back in and just cut the hose, its needed to cool the drive
 

achris

More fish than mountain goat
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May 19, 2004
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Doc is refering to water used to cool the exhaust gasses so they don't cook the drive as they pass through. You have raw water pick-up through the hull, but the 'used' water exits through the exhaust and down through the drive as per the 'normal' in-drive pump, so nothing to worry about.

Chris.....
 

Bt Doctur

Supreme Mariner
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Aug 29, 2004
Messages
19,092
achris, what I am referring to is the cooling water for the outdrive `s oil. Hot exaust and hot water exiting the engie go thru the outdrive to get out. That exaust water typically can be 160 degrees going thru the drive.
Without an impeller the water is only flowing freely thru the holes instead of being sucked in with a impeller.
Some people install drive showers to cool the outdrive even with an impeller
 
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