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Water pump failure questions

1999 7.4l I/O

Water pump was about 60hrs/2 yrs old when it failed. I have changed them regularly and having owned the motor a long time, it's occasional failure doesn't surprise me one bit.

That said, prior to noticing the failure after I pulled it out of the water and attempted to flush the engine, there was a unique symptom/sign of it failing that I haven't seen before, and Im curious if its common.

About 10 miles out from the marina, I had some fuel flow issues (indicated at least) in my flow scan gauge. Fuel flow began to become erratic, dropping to 3-4 GPH from about 16 at cruise. I never noticed the engine act up, just a indicated change.

Ultimately I want to know if anyone has seen this caused by a water pump starting to fail, as I have yet to see that prior to it failing?

It has a Fuel/Raw water pump combo of course, and the engine never changed normal operating temperature prior to pulling it out of the water and attempting to flush, when I noticed it was not pulling in water, and checked the impeller and found it had failed.

Any experiences with this would be interesting to hear.

Thanks
 
Could be a case of "Bravitiis"

While possible, the entire assembly (not sure what to call it) between the engine and the outdrive, including a lot of the upper part of the outdrive was replaced 2 years/60hrs ago due to corrosion caused by a long term minor leak in the speedo pickup tube. I imagine that hose/fitting is new, I'd have to check the specific part #s replaced from the receipt.

Any way to check without much drive disassembly?
 
It occurs at the gimbal side of the hose and the transom side of the hose
20160505_131422_zpstlomk8ic.jpeg

20160504_185108_zpsyyv4abc2.jpeg
 
Is this the Merc Seawater Pump that doubles as a fuel pump?
If so...... get rid of it and go to the crankshaft seawater pump and an alternate means for a fuel pump.

That seawater pump/fuel pump combo was as silly as Merc's attempt at the 3.7L Engine design.







.
 
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It occurs at the gimbal side of the hose and the transom side of the hose
20160505_131422_zpstlomk8ic.jpeg
20160504_185108_zpsyyv4abc2.jpeg
As far as I can remember all of that was replaced with the parts changed due to corrosion. That's said I'll check part numbers on the receipt when I can. That said I feel like it would be unlikely that the passage got narrow over time, as the temp of the engine isn't running any different than it has since it was new.
 
Is this the Merc Seawater Pump that doubles as a fuel pump?
If so...... get rid of it and go to the crankshaft seawater pump and an alternate means for a fuel pump.

That seawater pump/fuel pump combo was as silly as Merc's attempt at the 3.7L Engine design.







.

It's the combo pump

I'm not familiar with a crankshaft H2O pump, how hard is it to modify?

Would the current fuel pump work without the water pump or would an electric pump be a better alternative ?
 
The crankshaft seawater pump is very common among Volvo Penta, Indmar, PCM, Marine Power and more.
No modifications to the pump are required.

You must have enough space in front of the harmonic balance her for it.


Yes, the electric fuel pump is an option. However, you must also include the N/O low oil pressure switch and relay system in order to be legal.


.
 
Sorry Rick.


Leave the fuel Pump/Water pump Driver in place, There is nothing wrong with this set up. You have to check the gear lube in the driver when annually.
 
Sorry Rick.


Leave the fuel Pump/Water pump Driver in place, There is nothing wrong with this set up. You have to check the gear lube in the driver when annually.

Ive only had one other failure in 16 years of owning the motor, id say it's been pretty good to me.
Ill throw another pump kit in and see if the erratic indicated fuel flow continues, if not I'll assume it was associated with the Impeller failure.
 
Ive only had one other failure in 16 years of owning the motor, id say it's been pretty good to me.
Ill throw another pump kit in and see if the erratic indicated fuel flow continues, if not I'll assume it was associated with the Impeller failure.


Make sure the driver is clean and not in need of a rebuild itself.
 
Looking over the recipe from the item replaced due to corrosion, parts of the drive included

- Bravo Transom Housing
- Y-Pipe
- Bravo Drive Coupler
- Bell Housing
- Flywheel cover

I would imagine that the part that restricts water flow due to corrosion and is the cause of the "Bravoitis" was part of the "transom housing", can someone confirm that to be correct? The part number for that part is list as just "BRAVO"
 
Sorry Rick.


Leave the fuel Pump/Water pump Driver in place, There is nothing wrong with this set up. You have to check the gear lube in the driver when annually.

Chris, no need for an apology. I respect your experience, and I am certain that you have more experience with this particular seawater pump combo.
To the best of my knowledge, no other marinizing company has incorporated a similarily designed double-function seawater/fuel pump.

This is the style pump........ correct?

$_35.JPG


Myself..... I think that it's a silly design. Belt driven seawater pump owners tend to defer impeller maintenance due to the added difficulty of accessing the impeller.
If it was mine, I would see if the crankshaft pump could be an option, and if so, I'd go with the electric fuel pump (plus the required N/O LOPS and Relay).

Anyway...... I do wish the OP the best of luck.

Rick

 
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Chris, no need for an apology. I respect your experience, and I am certain that you have more experience with this particular seawater pump combo. To the best of my knowledge, no other marinizing company has incorporated a similarily designed double-function seawater/fuel pump. This is the style pump........ correct?
$_35.JPG
Myself..... I think that it's a silly design. Belt driven seawater pump owners tend to defer impeller maintenance due to the added difficulty of accessing the impeller. If it was mine, I would see if the crankshaft pump could be an option, and if so, I'd go with the electric fuel pump (plus the required N/O LOPS and Relay). Anyway...... I do wish the OP the best of luck. Rick
That is in fact the set up that I have. While I find it an annoying design, I don't mess with it enough for it to be too much of a hassle. I have plenty of room around the motor to work with it. An annual impeller change/oil reservoir drain and fill to prevent failure isn't too much of a hassle. That said I would still be interested in keeping a crank mounted pump / electric fuel pump combo in mind if needed.
 
Does that mount a mechanical fuel pump on the bare mounting face there? I assume GM dropped a mechanical pump off the block and Mercruiser must have had a lot of mechanical pumps still in inventory...
But if it works don't mess with it.
 
Does that mount a mechanical fuel pump on the bare mounting face there? I assume GM dropped a mechanical pump off the block and Mercruiser must have had a lot of mechanical pumps still in inventory...
But if it works don't mess with it.

It does mount there. Works great, Typically change the impeller annually. It has only failed twice in 16 years between preventative changes. Ill stick with the OEM set up for now.

Thanks the information everyone. Changed the pump, all is well now. Ill keep the modifications mentioned above in mind for the future if I need to change it up.
 
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