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Old 05-28-2014, 01:34 PM   #1
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Raw Water problem

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
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Old 05-28-2014, 02:20 PM   #2
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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?
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Old 05-28-2014, 03:28 PM   #3
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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
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Old 05-28-2014, 03:33 PM   #4
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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
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.
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Old 05-28-2014, 03:35 PM   #5
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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..
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Old 05-28-2014, 03:39 PM   #6
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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.
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Old 05-28-2014, 03:42 PM   #7
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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...
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Old 05-28-2014, 03:45 PM   #8
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If it is a belt driven pump, be sure the belt isn't slipping.
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Old 05-28-2014, 03:48 PM   #9
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Hadnt checked that... would it be visibly slipping, or would I hear it?
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Old 05-28-2014, 03:50 PM   #10
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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.....
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Old 05-28-2014, 03:58 PM   #11
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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.
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Old 05-28-2014, 04:06 PM   #12
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Have you checked your heat exchanger to see if it is clogged?
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Old 05-28-2014, 04:38 PM   #13
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He has a Perkins NA 6.354.


Should be a Jabsco pump. That's what I have on both of mine.
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Old 05-28-2014, 04:41 PM   #14
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Quote:
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Have you checked your heat exchanger to see if it is clogged?
I thought of that... but would the heat exchanger blockage stop the water form coming in to the impeller...
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Old 05-28-2014, 04:42 PM   #15
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He has a Perkins NA 6.354.


Should be a Jabsco pump. That's what I have on both of mine.

Yeah, i put one in and it matched the one i took out exactly...
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Old 05-28-2014, 05:31 PM   #16
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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?
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Old 05-28-2014, 05:34 PM   #17
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The inside of the houseing was nice and smooth
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Old 05-28-2014, 05:40 PM   #18
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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.
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Old 05-28-2014, 05:53 PM   #19
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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?
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Old 05-28-2014, 05:53 PM   #20
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Quote:
Originally Posted by superdiver View Post
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
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.
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