Raw Water problem

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superdiver

Senior Member
Joined
Jun 27, 2013
Messages
120
Location
Ketchikan
Vessel Name
Nimbus
Vessel Make
Californian
So i changed out the impeller and thru hull valves this last pull out.

Changed all the fluids and filters etc....

Both engines run better then ever EXCEPT, the strbd side is not pulling the raw water thru.

I put in qtr turn valves and cleaned the strainers too. I KNOW water is getting in and to the strainer and that the valve is on (I always try to check the stupid easy stuff first).

I did have to change the gasket on the impeller, and I think the one i used was a little thicker then the original that was so bad I couldnt tell what they used.

I am pretty sure its an air bubble somewhere, but I cant seem to find a way to "prime" the system and make the impeller pull water thru.

I know I ran the engine untill it got up to just over 170 (on the temp gauge) and shut it down as it was warming up too fast and I suspected a problem. I assume doing this ruined the impeller so I plan to change that again tonight.

But I was wondering if there was something stupid I may have missed, or an effecient way to "prime" it, although I wouldnt think i need to "prime it"???

any and all help appreciated, dont leave out the stupid questions as I OFTEN miss those...LOL
 
Greetings,
Mr. s. Was the old impeller in one piece? Did you check your coolers for restrictions/blockages? Did you lose cooling water prime in the "offending" engine?
 
Yes, all in one piece, no tears or anything visable. People told me once you run it without water you HAVE to replace it... how true is that?

As far as losing prime, I am SURE thats what happened. I tried priming it into the top of the thru valve as I put in a "T" with that need in mind, I also tried priming it thru the supply hose to the impeller, but no luck there either.... I am SURe its a priming problem, i just cant figure out how to REprime it
 
superdiver said:
Yes, all in one piece, no tears or anything visable. People told me once you run it without water you HAVE to replace it... how true is that?

As far as losing prime, I am SURE thats what happened. I tried priming it into the top of the thru valve as I put in a "T" with that need in mind, I also tried priming it thru the supply hose to the impeller, but no luck there either.... I am SURe its a priming problem, i just cant figure out how to REprime it
Click to expand...

Did you check the impeller Spline shaft? It could need a rebuild. Mark the impeller after you install it say at the 12 o'clock position. Run the motor up and then pull the cover off to see if pump is turning. Also you should see the water in the exhaust.
 
I checked the impeller and it is running (turning) fine, very little raw water comming out of exhaust and the opposite engine has exact same set up and has tons of water coming out..
 
Shouldn't have to prime a flexible impeller water pump....it may very well be that thicker than normal gasket.

Old timers would use a paper shopping bag with a few drops of oil on it...they just put a piece over the whole pump and impeller, bolted the cover on and let her rip. The paper covering the impeller would just tear away and the part that was snug under the cover/edge of pump would remain and do it's job...been meaning to try it as gaskets are a PIA sometimes if they get a crease in them.

You might want to try that if nothing else works and you don't get the right gasket.
 
Thats sounds VERY much like what was there... I will for sure try that as the thinnest gasket material i could get in town was quite a bit thicker then what was there...
 
If it is a belt driven pump, be sure the belt isn't slipping.
 
Hadnt checked that... would it be visibly slipping, or would I hear it?
 
I always oil the paper gasket up a bit so it's easier to get off...any motor oil does the trick.

What engines? sorry if I missed it someplace.....
 
Might be a good idea to call the very knowledgeable folks at Depco Pump. Do you have any idea what kind of pump it is? If not, they can probably figure it out from the year and model of your engine. Get you the right gasket and/or other parts needed. Have you checked the wear on the cover plate? On many of them, you can flip it over and have a new surface, but make sure you have a pump that can do this. Without knowing more about your engine, pump and boat configuration (such as how high above the waterlie your pump is), hard to give advice. But typically RW pumps with flexible impellers are self priming.
 
Have you checked your heat exchanger to see if it is clogged?
 
Here is a simple test. Stick a hose in a 5 gallon bucket of water and then hook that hose to the inlet side of your raw water pump. Turn the engine on, if the pump does not draw water from the bucket after a few seconds then the impeller housing in the pump body is more than likely shot.

That pump is self priming and if the cooling system is open and clear down stream should have no problem priming and pumping water through the engine.

What does the side of the impeller cover facing the impeller look like? Is it very worn and grooved?
 
one more possibility is the wear plate inside the pump...it's usually slotted and what bends the impeller vanes to cause pumping...make sure it's there and looks "OK"..if you don't know "OK" you can look at your other one or a pic of one and guess.

My guess is that if it was working well before the impeller change...it's gotta be the gasket unless that wear plate fell out somehow.
 
The wear plate is the part that bends the blades and "pumps" the water out, correct? We noticed that part and as we had never taken one apart we "conjured up" that that was what it did... Doesnt look like it can come out on mine... but it may... it certainly didnt come out while it was apart...

All good ideas guys.. keep them coming.. I want to make sure I cover everything...

I am considering adding a "T" to the supply hose to see if I can get it to prime that way...? what do you think that sounds like?
 
superdiver said:
So i changed out the impeller and thru hull valves this last pull out.

Changed all the fluids and filters etc....

Both engines run better then ever EXCEPT, the strbd side is not pulling the raw water thru.

I put in qtr turn valves and cleaned the strainers too. I KNOW water is getting in and to the strainer and that the valve is on (I always try to check the stupid easy stuff first).

I did have to change the gasket on the impeller, and I think the one i used was a little thicker then the original that was so bad I couldnt tell what they used.

I am pretty sure its an air bubble somewhere, but I cant seem to find a way to "prime" the system and make the impeller pull water thru.

I know I ran the engine untill it got up to just over 170 (on the temp gauge) and shut it down as it was warming up too fast and I suspected a problem. I assume doing this ruined the impeller so I plan to change that again tonight.

But I was wondering if there was something stupid I may have missed, or an effecient way to "prime" it, although I wouldnt think i need to "prime it"???

any and all help appreciated, dont leave out the stupid questions as I OFTEN miss those...LOL
Click to expand...

This pump type is working with vacuum and not as paddeltyp. When the side pressure from the impeller is not good the vacuum pump is not operating.
check the seal and see if the plate is completely smooth.
__________________
Norbert
 
superdiver said:
The wear plate is the part that bends the blades and "pumps" the water out, correct? We noticed that part and as we had never taken one apart we "conjured up" that that was what it did... Doesnt look like it can come out on mine... but it may... it certainly didnt come out while it was apart...
Click to expand...

The wear plate is behind the impeller and is usually stainless steel, if your pump is a Shurwood, it doesn't have one. The part you are talking about is the cam. If it was removed, it should have sealant, gasket cement put on it where it meets the housing. Otherwise it can draw air under it and keep you from priming up quickly.
Make sure the pump cover is refinished flat and your gasket is no thicker than a greased phome book page. Then start looking for a suction leak between the pump inlet and the thru-hull. Even a small one can upset priming your system if your pump is weak.
 
Brooksie said:
The wear plate is behind the impeller and is usually stainless steel, if your pump is a Shurwood, it doesn't have one. The part you are talking about is the cam. If it was removed, it should have sealant, gasket cement put on it where it meets the housing. Otherwise it can draw air under it and keep you from priming up quickly.
Make sure the pump cover is refinished flat and your gasket is no thicker than a greased phome book page. Then start looking for a suction leak between the pump inlet and the thru-hull. Even a small one can upset priming your system if your pump is weak.
Click to expand...


All I removed was the over plate and the rubber impeller, everything else was as it was before.

I have a feeling its the gasket or and air leak like you said.


The other possibility I am leaning towards is that the ball valve i put in is taller then the old failed gate valve i replaced... but I did the same to the other engine and I would think that it would have the same problem too if that was the case... they are mirror images of each other...
 
superdiver said:
The other possibility I am leaning towards is that the ball valve i put in is taller then the old failed gate valve i replaced... but I did the same to the other engine and I would think that it would have the same problem too if that was the case... they are mirror images of each other...
Click to expand...

Unless the valve is now above the water line, which I highly doubt, that is not you're problem. And even if it was the pump should have no problem sucking up water from it to prime it's self.
 
The real question is; did the engine and pump work before you worked on it?

If so, the problem is not caused by wear, it's something you did. Go back and check your work. Check it again if you have to. Have someone else check it.

Did you change the gasket on both pumps? Did you use the same type of gasket? If so and one works, it's not the gasket.
 
rwidman said:
The real question is; did the engine and pump work before you worked on it?

If so, the problem is not caused by wear, it's something you did. Go back and check your work. Check it again if you have to. Have someone else check it.

Did you change the gasket on both pumps? Did you use the same type of gasket? If so and one works, it's not the gasket.
Click to expand...


Thats what I believe! And thats my usual operating motto.. I ALWAYS figured it was something I screwed up...LOL It was totally working BEFORE I messed with it...

Only changed the gasket on the one pump (not working now) and had the water lines off the one non functioning cooling system.... so my plan is to replace the gasket with the MUCH thinner one made of something like a phone book page and oil (as thats what the old one looked like when we removed it, we remarked at how "bogus: it was cuz it was so thin...LOL) and I will tighten up the hose clamps to make sure its not leaking...

I also added the new ball valve which is a bit taller then the old Gate valve. But I changed that on the other one as well. The taller aspect may be a problem, but the other side is identical and it works fine...
 
Seems to me that if the strainer is filling, then the new valve must be working. I'd test the pump output by pulling the discharge hose off for a minute & running the engine; flow should be good. If not I'd suspect the gasket. If flow is good, you may have blockage elsewhere. The unit has to have a good side seal inside the cover plate to work well. I had to use RTV once as a seal to get home. Until we really squeezed it down, the pump was not very effective. Botrh Jabsco & Sherwood sell gasket kits for most of their pumps; online, or @ WM
 
Try putting the plate on without a gasket. It will leak a little, but you can the easily verify it was the gasket and replace it. If that doesn't solve the problem, try reassembling with the old impeller to rule out the new impeller.

Ted
 
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