help with no raw water flow

[Gary Ambrose]

We have an 86 with an M-25. It has the Oberdorfer water pump. Can not seem to get raw water to flow for cooling. Here is what I have done so far.

1. replaced impeller and gasket
2. primed intake hose
3. bypassed the strainer by placing raw water pickup in a bucket.

Still no pick up of raw water.

I have heard that .004 thousandths wear on the cover plate could be the cause of no suction.

Any one with a similar experience? Any ideas much appreciated!

[Randy Stolze]

Gary,

     How did the old impeller look when you took it out? Was it missing any blades? Did you check the flow through the heat exchanger?

     I smoothed the face of the pump cover by using 220 grit wet sandpaper. Put the sandpaper on a known flat surface,ie. glass, marble coffee table etc. Keep the sandpaper on the flat surface, grab a beer and go at it. If you have deep score marks in the cover grab two or three beers.

  Smooth Sailing!

  Randy

[Ron Hill]

Gary : Do as Randy mentioned.  
You didn't say if you have a paper thin gasket on the face plate. That's very important.  
Take some water resistant/proof grease and place a light coating on the face plate and on the inside vertical portion that the side of the impeller blades ride on.  This creates a better seal and decreases the wear on the face plate and inside pump housing.  
Keep us posted.  

[Gary Ambrose]

Hi Randy and Ron,

Thanks for the great tips! Sanding with 220 wet/dry on glass sounds like a terrific tip.

Ron: I did use a paper thin gasket....it is the gasket supplied by marinedieseldirect.com for Oberdorfer pumps. And I did use some water resistant grease inside. I will flatten the cover per Randy's suggestions and then use a good coating of grease on the cover.

By the way. The impeller was not missing fins and looked to be in good shape. I replaced it anyway and will keep the old as a backup. The cover plate shows no sign of scoring but shows a very slight wear at the shaft contact area. Of course what looks flat and is flat are quite different. The cover looks pretty good. So that is where I'm at.

I'll keep you posted on final solution.

Thanks for the support and terrific suggestions!!

[Ron Hill]

Gary : Don't over grease, as it can clog up the water lines and the inside of the heat exchanger.
You might try to blow thru the line to the heat exchanger and see if it's free.  Also suck water thru the line from the raw water thru hull to the Oberdoffer and make sure it's free.  
I know you said that the inlet raw water line was primed, but try this procedure anyway:
It takes 2 people.  Open the thru hull and disconnect the inlet line to the Oberdoffer.  Take a little Jabsco pump and insert it in the raw water inlet line.  Start to suck water thru the line by pumping it into a bucket.  As the water flows, tell the other person to shut off that thru hull while you hold that line up.  Remove the pump, put your thumb over the hose end and reattach it to the Oberdoffer.  Open the thru hull, start the engine and the water should spit out of the exhaust.  Try it.  

[Tom Glennon]

Tom here from Buzzards Bay... regarding the raw water flow (or lack thereof...) I would open the face of the pump with the sea-cock closed, then open the sea-cock to insure water is flowing to the pump.  Insure the "key" is there in the shaft of the water pump and that it engages the impeller, so that the impeller will rotate when the shaft turns.  Good luck!

[Gary Ambrose]

Raw water problem solved !  The sea cock below the raw water strainer had a single small muscle that collected seaweed and blocked water flow. With the strainer unscrewed from the sea cock and the sea cock open there was no water flow. It was packed tight.  A 5/8" dowel cleaned the hole, plus embedded muscle, from the sea cock, and we had 9" of water squirting in at the sea cock. Yahoo!

Next we found the best way of getting water through the pump and lines was to take the out feed from the Oberdorfer off and run the engine for 10 seconds until there was a strong flow. After reconnecting the outflow line and restarting the engine it took awhile (45 seconds) before raw water appeared from the stern exhaust. It is a small pump and there are a lot of lines to fill and purge air. But, we are going strong with great water flow again.

Thanks to all and help reaching another point on the learning curve for our C34!

[Ron Hill]

Gary : Hurrah, you found the problem!!
I believe that you would have found it had you try-ed to suck water up to the pump as I suggested.  It's imposable to "prime" the inlet hose by trying to fill it with water - you need to pull it up and then shut off the thru hull (hence the need for another person).

Why make the pump work so hard when it's dry, when you can pull water up and IMMEDIATELY have water spitting out of the exhaust - no need to rev the engine!!  Try it the next time you change/inspect the impeller - try it you'll like it.  

[Gary Ambrose]

Ron,

You are right and thanks for the reminder about using a jabsco pump to draw raw water through the line after the pump. Sometimes it takes awhile for good ideas to penetrate.

Do you have a jabsco pump recommendation??

What are the other uses you find for your pump?

Thanks very much for your good work!

[Ron Hill]

Gary : I've had a Jabsco "Little Pal Hand pump" for 18 yrs and use it for many things.  (West marine page 350)
I fill the Xmission with oil to the top (per manufacturer's instructions) for the winter layup and suck (Little Pal) all of the fluid out in the spring and refill to the correct level.
Anytime I drain the internal fluid (for MANY reasons) I suck the internal coolant out of the water heater line and use the Little Pal to "burp" the system.
Used anytime I fool with the raw water pump and every spring to get the water back up to the Oberdoffer it gets sucked up with that pump.
These are just some of the things I can think of that I use that pump for. A great investment!!