No flow from water pump

[gohawks688]

1987 omc 3.0 w/ cobra outdrive fresh water cooled

ok omc experts lend me a hand here. I have no raw water flow. It's causing overheating. (Obviously)
Diagnosis: zero raw water flow. Tested with boat in the water. Input hose to heat exchanger removed no flow.
New impeller installed w/ permatex aviation sealant. Allowed to set up over night.
Water pump shaft verified spins.
System flushed for blockages with garden hose (impeller and housing removed) great flow from both inlet and outlet side of water pump intakes.
i can run the boat off the muffs but i really have to press the muffs on the drive to force water into the pump. (To prime it?)

So guys what's the deal? I have been scouring the threads. This all started when I swapped out my drive with a craigslist unit due to dog clutch slippage. My guess is there is a seal in the drive that is allowing the pump to suck air? Or have exhaust intrusion? This issue only started when I put the craigslist drive on so it has to be something with that and not the motor / heat exchanger/manifolds.

​​​​​​Any ideas? Thanks!

 

[gohawks688]

So I have been thinking about this more... The seals in the drive... should they matter at all when the drive is submerged ( not on plane). with the drive fully submerged there should be no air to suck into the pump? How can i be getting zero water flow?

when i flushed the system i removed the pump/housing and used the muffs to flush up into the drive and out the pump intake. I also flushed from the boat side out the pump intake (through heat exchanger) I had good flow on both these test so I dont think there is an obstruction.

I don't think there is a way to install the impeller wrong. I did reuse the impeller/housing from my other drive (that didnt have a water flow problem). the impeller is one year old. not brittle. the housing/wear plate is in great condition no scores or warping.
I verified that the shaft spins.
I greased the impeller/metal cup.
The vanes of the impeller will flip to what ever direction the pump spins so i didn't install in the wrong orientation.
I used permatex and the o-ring is in place.
No water squirting from around the pump housing
Once primed on the muffs water squirts from hose on left hand side of pump housing (when removed)

 

[kenny nunez]

There is a grommet that is in the upper gearcase where a copper pipe connects the 2 halves together. You need to remove the drive an separate the upper to the lower. That is about all I can think of.

 

[jc turtle]

Hi gohawks, my son had the same problem 3 weeks ago. It turned out to be a 1/4 inch hole in the pipe that kenny mentioned in the above answer. We had replaced some parts and still had the problem.. We were so happy when we found that hole in the pipe. We knew we weren't chasing a water ghost. Pull both halves of the outdrive apart and check that tube.
Good luck, John

 

[gohawks688]

Hi gohawks, my son had the same problem 3 weeks ago. It turned out to be a 1/4 inch hole in the pipe that kenny mentioned in the above answer. We had replaced some parts and still had the problem.. We were so happy when we found that hole in the pipe. We knew we weren't chasing a water ghost. Pull both halves of the outdrive apart and check that tube.
Good luck, John

Turtle did you have the problem with the drive in the water fully submerged? I hope my problem is that obvious when I get in there. It sure does feel like I am going crazy!

Awesome I will drop the drive and split the case and check out that pipe. I have three drives on hand so hopefully I will have the parts on hand to fix it!

Besides the pipe andrand grommet are there any orings that contribute to this seal?

 

[jc turtle]

Yes, the engine would overheat after idling in the ocean at the dock after 10 or 15 minutes. I ordered a lower unit seal kit and replaced all the o rings and gaskets that I could easily get at. Good luck, John

 

[gohawks688]

Well guys I split the case. Found some damage to one of the grommets on the lower. Copper pipe seemed to be in good shape. Going to put it back together with seals from another lower I have that pumps good. Will use gasket sealant on the grommets to hopefully create a good seal.