water pump not drawing water

[tom475]

I just installed a new impeller and gasket and I'm not drawing any water.  I blew both intake and out lines clear, no debris in either one, cleaned intake strainer, intake strainer is full of water. Any suggestions?

[Roger Blake]

Most likely, you have an air lock...need to get all air out of the system.

[Ron Hill]

Tom : The next time you decide to check the impeller or change it Turn Off the Thru hull FIRST so 95% of the water in that line stays there!!

What you've done is you have lost all of the "prime" water in the inlet hose.  Fill the hose with water (thru hull off) or suck water thru the inlet line until it comes out (shut off the thru hull) and then reconnect the hose to the engine pump.  Open the thu hull and start the engine, you may have to give it a frw revs.

Hope this helps.  

[Stu Jackson]

Is the inside of the faceplate smooth?

[Ron Hill]

Guys : Stu brought up a good point that if the inside of the face plate has wear groves, then the suction of the pump lessens. If you follow the inlet hose it goes from the thru hull up above the water line above the engine and then down to the pump on the engine - about 5 or 6 ft of hose.
If that hose is empty it takes some real pull to get the water to the pump!!  

I've noticed that with the Sherwood (which pumps more water) that the startup after a impeller inspection/change is more apt to pump water right away than with the Oberdoffer. I don't have to replace the prime after winter storage.  

Regardless, I still shut off the thru hull before removing the pump housing/face plate.

A few thoughts

[Stu Jackson]

The only time(s) I've ever had prime problems were the faceplate.  The pump is under the waterline.

[tom475]

The face plate is smoooth, I closed the seacock and removed the intake line from the pump, it did not talk much water to fill the line, opened the seacock still no water flow.

[pablosgirl]

Hi,
Could this be the case of the face plate gasket being to thick and the impeller not making a good seal against the face plate?  I seem to remember a thread about that cause a couple of years ago.  Try a search or may be Stu or Ron remember the details more clearly.
Paul

[Stu Jackson]

The face plate is smoooth, I closed the seacock and removed the intake line from the pump, it did not talk much water to fill the line, opened the seacock still no water flow.

Only three things between the water and your pump:  hose, strainer and thru hull.

Check them all out.  You can back-pressure the thru hull with a dinghy foot pump from the hose at the pump.  Take the strainer off - do you get water?  Take the hose off at both ends and blow through it.

What else can it be?

[Clay Greene]

You said that you replaced the impeller - did you get all the fins from the old impeller?  We had an overheating issue that we inherited from PO and we found impeller fins in the 90 degree elbow that connects to the hose to the heat echanger, in the end of the hose at the heat exchanger, and in the heat exchanger itself.  We were still pumping water but at a rate of less than half of what we had when we removed all the obstructions.

[Ron Hill]

Tom : I must have missed your post, but if the face plate is smooth and you used a paper thin gasket - here are a few more ideas :  (I assume you have an Oberdoffer?)

1. Remove the face plate and make sure that the impeller is seated on the shaft and the shaft is seated in the notch inside the engine - so the impeller rotates when the engine is cranked.
2. Remove the hose from the pump intake (with the thru hull open) and blow out that inlet line.  Then be sure to refill that line before cranking.
3. Check the output line of the pump (and as mentioned the 90 degree elbow) and make sure it it clear.
4. Be carefull that you are not filling the muffler with too much water.

Hope this helps

[Michael Shaner]

Tom, a freak thing happened to me causing just such a situation. Had it not happened to me, I wouldn't believe it. I had a failing O ring on the strainer...failing just enough to cause the pump not to prime, yet did not leak when the thru hull was open. Shortly there after, the same thing happened to the prime on the fresh water pump, then the AC pump...like within a week. All were identical strainers of apparently the same vintage. Who'd a thunk it. Give it a whirl...may cost a buck fifty at the hardware store...

[tom475]

OK guys it's the weelend and I decided to try again, I replaced the raw water strainer since I didn't trust the gasket, I opened up the pump (Sherwood ) and replaced the paper gasket, I filled the hose and opened the sea cock, still no water out the exhaust.  Now what?

[Ron Hill]

Tom : I'm guessing that you have the older Sherwood with a face plate?  
If you do, close the thru hull, remove the face plate and insure that the impeller and shaft are fully seated.   Have someone else crank the engine over so you can see if the impeller is turning when the engine turns over.  You don't want the engine to start so to insure that it doesn't start have that person crank with the engine kill handle pulled out (or you can do that at the engine).

Also check to make sure that the impeller has a flat slot where it mates to the flat spot on the shaft shaft.  Check to make sure the inside bronze piece inside the impeller is still molded to the impeller.

We are just trying to make sure that when the engine turns the impeller turns.  Ckeck to make sure that you have the correct impeller and/or reinstall the old impeller (if the old impeller was working when you decided to change it!!).

If the impeller turns when the engine is cranked - Then lightly grease the inside of the pump housing, seat the impeller, replace the face plate, re-prime the intake hose, open the thru hull and start the engine. Rev it a couple of times and exhaust water should come out.

[tom475]

Ron,
I've done all of the above and still no water.