I just repaced my Yanmar engine water pump with a rebuilt @ $275! Seems it should pump water instead of air---I have no exhaust water, yet air bubbles come up from the water intake...my wife suggested that the impeller may be reversed---is that possible (or is there an air lock in the system. Please respond---Thanks
engine water pump
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If the rebuilt is the same as the original, it seems they should rotate in the same direction. You could remove the hose connection from the intake side of the pump and see if water is flowing. In most installations the water from the intake should flow to the pump without having to pump/pull it thru the hose. If you have water to the pump can you disconnect the hose to the engine and see if water is being pumped through?
couple things to check. First, if it is a new or rebuilt pump that came with an impeller, odds are it was installed correctly. So, did you check your raw water strainer? When you replaced the pump did you take apart the old pump to make sure the impeller is still intact?
compare your new pump to the old. see if the cam (inside where impeller is) of the new is side location as old. i believe this cam can be mounted top or bottom depending on the inlet/outlet barb and rotation direction of pulley. to prime the pump, what i normally do is fill water to the pump discharge hose (the connecting to the heat exchanger) till full then connect back to HE and run the engine.
Well, not being familiar with this particular engine or pump, I'll take a guess and say that somehow the inlet and output of the pump have been interchanged.
If the cam inside of the pump can be positioned at the top or bottom, that sounds like the pump can be configured to pump in either direction. I would agree with Ken13559 that it may be in the wrong position for this particular engine.
I have never seen a rubber vane pump that needs priming if the impeller is in good shape. These pumps self-prime.
A last note- if the cam in the pump is in the wrong position causing the pump to pump from the output to the input, then I think it could pull air from the exhaust through the heat exchanger and push it into the strainer and out the thru-hull. This would coincide with your observed scenario. Also, if that is the case, that means that the impeller has been run dry without water lubrication and is probably toast. When you open the pump to check the cam position, be sure to check the condition of the impeller.
If the cam inside of the pump can be positioned at the top or bottom, that sounds like the pump can be configured to pump in either direction. I would agree with Ken13559 that it may be in the wrong position for this particular engine.
I have never seen a rubber vane pump that needs priming if the impeller is in good shape. These pumps self-prime.
A last note- if the cam in the pump is in the wrong position causing the pump to pump from the output to the input, then I think it could pull air from the exhaust through the heat exchanger and push it into the strainer and out the thru-hull. This would coincide with your observed scenario. Also, if that is the case, that means that the impeller has been run dry without water lubrication and is probably toast. When you open the pump to check the cam position, be sure to check the condition of the impeller.
Thanks for your help guys...I need to check the raw water strainer to insure it is full of water. a lot (quart) drained out while I changed the pumps.
Which engine do you have in your 34?
I rebuilt my raw water pump on my 3GM(F) recently (for about half of what you paid for the rebuild - you got a good price). I did it on my living room table with little more than a hammer and screwdriver (and some muscle). It was pretty foolproof.
The impeller can't go in "backwards" but it could go in upside down. Can't see how that would make the pump run in reverse. Seems more likely that you installed the pump onto the engine backwards (which I almost did). That's why I ask for the model number. Or a good, clear picture.
Last option depends on how many bubbles you're getting. If it's lots, then I suspect the installation. If it's just a few, maybe they're from something else and your intake seacock is still closed... (oops).
I rebuilt my raw water pump on my 3GM(F) recently (for about half of what you paid for the rebuild - you got a good price). I did it on my living room table with little more than a hammer and screwdriver (and some muscle). It was pretty foolproof.
The impeller can't go in "backwards" but it could go in upside down. Can't see how that would make the pump run in reverse. Seems more likely that you installed the pump onto the engine backwards (which I almost did). That's why I ask for the model number. Or a good, clear picture.
Last option depends on how many bubbles you're getting. If it's lots, then I suspect the installation. If it's just a few, maybe they're from something else and your intake seacock is still closed... (oops).
A closed seacock is likely to shred you new impeller to bits if you let the engine run for any significant amount of time, so make sure it's open and the strainer is clear.
I read somewhere that little bits of shredded impeller bits can go through the water pump and get lodged in the heat exchanger thus preventing proper water flow.
If your hoses are not kinked and the strainer is clear and your seacock is open, I would suspect a blocked heat exchanger.
good luck.
I read somewhere that little bits of shredded impeller bits can go through the water pump and get lodged in the heat exchanger thus preventing proper water flow.
If your hoses are not kinked and the strainer is clear and your seacock is open, I would suspect a blocked heat exchanger.
good luck.
Another thing...
you may need to do after having the pump off is to "burp" the water line to get the air out that got in when you pulled the pump (air lock). Pull off the water hose leading to it and have someone open the seacock until water comes out. Clamp the hose back on and fire her up. You should now be pumping water!
The impeller vanes will align themselves no matter which way you have it installed when the pump spins.
you may need to do after having the pump off is to "burp" the water line to get the air out that got in when you pulled the pump (air lock). Pull off the water hose leading to it and have someone open the seacock until water comes out. Clamp the hose back on and fire her up. You should now be pumping water!
The impeller vanes will align themselves no matter which way you have it installed when the pump spins.
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