Urgent - Raw Water Pump Not Working!

[unbusted67]

Hang in there Don. You will figure it out sooner or later.

After reading this thread I am thinking seals on the impeller housing but that's just a random hunch. It seems like, if what caused this was an extreme jarring motion from a wake then you should be looking and thinking about things that could have been shock loaded and damaged. I wonder if a sudden surge of water pressure on the low pressure side of the pump could have done some harm?

Any way keep your wits about you and for god's sake don't call a mechanic!

[Don1500]

for god's sake don't call a mechanic!

Last,.... very last resort. I still have skin left on my finger tips, and my hands aren't too cut up, so I can take the pump apart a few more times.

[jacob30]

I still think it could be the water pump">raw water pump. The shaft may still turn if it is bad just not enough to supply water. A visual inspection of it as you start the engine is still needed.

[Ex-Calif]

Originally Posted by Don1500

Last,.... very last resort. I still have skin left on my finger tips, and my hands aren't too cut up, so I can take the pump apart a few more times.

Sometimes it is helpful to restate the problem.

- you were running fine
- a large wake rocked your boat
- the raw water stopped pumping

It is either a correlated failure not related to the swamping or it is correlated to the swamping.

The water flows through a throguh hull, to a strainer, to the inlet of the raw pump. After the raw pmp it goes to a vented loop, then the heat exchanger, then to the exhaust system.

The inlet is clear up to the strainer. The strainer is full of water.

- remove the hose on the raw water inlet. Is ther water in this hose?
- change the impeller for your new one - may as well elliminate the impeller once and for all
- check very carefully the seating of the impeller cover and the key on the impeller. Assure yourself there is no spacer or other item that fell out of the impeller housing that spaces the impeller. Measure or eyeball the depth of the housing compared to the thickness of the impeller. We are trying to elliminate a poor fit or any other impeller issue.
- if all that checks out
- make sure the anti siphon is not stuck open. Strange as this is on the pressure side of the raw pump so shohuld not be a factor
- finally you will have to start checking for blockages on the pressure side

With the pressure hose off the pressure side to the exchanger you should be pumping tons of water. This leads back to a failed impeller. This system is too simple to have a complex failure.

[Blue Stocking]

Check the hoses from inlet to strainer, and strainer to pump. Re-inforced hose has a rubber inner liner which sometimes seperates, and collapses under vacumn, blocking water flow.

[svHyLyte]

Ensure that your raw water strainer is not leaking air. A friend of ours had a similar situation develop with his 4-108 and went through what you're going through. He had a Vetus plastic strainer and I discovered that it was leaking air around the top seal. A little silicon temporarily solved the problem but he eventually had to replace the strainer.

FWIW...

[Ziggy]

Originally Posted by delmarrey

Rubber impeller pumps don't need a prime.

That is not true in my experience. Some do, some don't. You should try smearing a bit of silicone grease over the impeller blades and checking if this will fix it. Silicone dielectric grease used for electrical connections will do; if you don't have any, you can try using some dishwashing detergent. Even butter or margarine might work. Don't use petroleum based grease on any rubber parts.

The other likely possibilities are an air leak in the raw water strainer (you can check that by taking off the hose and trying to suck from a bucket (make sure you have that grease on the impeller) and a delaminated impeller bushing.

This last one may be difficult to diagnose--the impeller looks intact, and there is still enough friction between the rubber and the bushing to make it difficult to turn. On mine there is a little screw in the bushing that aligns with a hole in the rubber; if the screw head is offset from the hole in the rubber you know the bushing is delaminated.

A likely failure scenario in your case is that when you were hit by the wake, you may have gotten air into the raw water inlet and the impeller lost prime and ran dry for some time, causing the bushing to delaminate.

Good luck!

[Don1500]

Items done today:
1. New Impeller, Used supplied Impeller Lube ( I guess this would be the right stuff to use.) I now have three spare impellers (Bought 2 today and the one I can't find.)
2. Blew bubbles outside the boat by blowing on the hose from the inlet to the pump.
3. As an add on to that I closed the sea cock and could not blow anything (check for leak).
4. Checked that the shaft was turning (it is) and found the direction of rotation was opposite to what I thought. Pulled the impeller and reversed the direction of tilt on the vanes.
5. Replaced the internal; delrin bearing and the metal cover plate. Also the gasket.
6. Tightened every belt connection.
7. with the input hose disconnected tested to see if there was suction into the pump, none, but I don't know if this is a valid test.
Final results after putting it all back together (for the 15th time) No water out the back.

Next on the agenda I will close the sea cock, remove the input hose and fill it with water and reconnect it. Start the engine and open the sea cock. But that is for tomorrow. I am staying another night.

[Don1500]

On a side note, the heater pump is working again. I cleared a blockage and now it runs fine. And the raw water pump isn't listening to this.

[atoll]

looks like you have tried every thing bar fully priming the system,back from the anti siphon.
are you sure you havent switched over the inlet and outlet hose's

the next test you could do is with a bucket and two bits of hose on the inlet and outlet of the pump,and see if water circulates

[Ziggy]

This is truly bizzare. Sounds like you have tried almost everything (Atoll's suggestion is good.)

The only other thing I can think off is to take the cover off the pump and try to turn the engine over and see if the impeller moves.

[travler37]

Sounds like you have tried all.
Input hose is colapsing on the inside.Leave strainer open and fire it up.Dump a bucket of water in it and see if it sucks.Repeat going down the line to pump......
Good Luck
Mark

[DeepFrz]

I would suggest you review Main Sail's article on replacing an impeller.

Changing A Raw Water Pump Impeller Photo Gallery by Compass Marine at pbase.com

Also, have you checked the input hose to make sure the inside is not collapsing and blocking flow? I would also suggest you try as others have suggested and disconnect the output hose, fully prime the pump and then turn the engine over with the cut off valve closed and see if the pump moves water. If not you have a bad pump.

Check to make sure the interior ramp (cam) that compresses the vanes has not fallen out. The ramp is necessary for the pump to move water and must contact the vanes after they have passed the outlet port of the pump.

[bill352]

Not exactly sure of the sequence of things, but if you installed the impeller with the vanes in the wrong direction, then ran the engine, then found the vanes still the wrong way, it is possible the shaft is not turning the impeller. They will usually straighten out on their own after a couple of turns.

[Ex-Calif]

Originally Posted by Don1500

On a side note, the heater pump is working again. I cleared a blockage and now it runs fine. And the raw water pump isn't listening to this.

Wow! Stay patient Don. This will make a great story someday...

We are in the realm of the crazy at this point.

- I agree with Atolls suggestion to isolate and submerge inlet and outlet hoses in bucket and see if raw pump circulates.
- I haven't seen or missed whether an upstream air leak has been eliminated. Does the raw water strainer have a bleed valve on top? Is this valve closed?
- remove hose to stainer inlet and run wire coathanger down it to check for blockage?

Isolating the raw pump at this point will eliminate it as a factor, then it seems you are back to blockages. Your blow test seems to verify everything from the strainer to the exhaust port but unless I read incorrectly does not preclude a blockage or leak from the strainer back to seawater inlet cock.

One thing for sure is it has to be something!