priming a raw water impeller

[Don Crowther]

The ice is off the lake the docks are in and we have launched!!:dance:
But as we started the engine no water was coming out with the exhaust.

I did have the impeller out and replace the hoses from the strainer to pump. I've checked the seacock and the strainer is still full of anti-freeze. Will i have to prime the pump to get it going?

I did move the boat under it's own power to our slip (about 3-4 minutes from launch site). Would there be any damage done by doing this?
I won't be able to get back to the boat until next weekend. Any suggestions on what I should be looking at? Should i remove the pump and check the impeller? Just a note it was working fine last fall. But this is a new boat for us and I was just checking everything I could before the summer begins

thanks as always
Don

 

[Don S/V ILLusion]

You need to inspect the impeller now to make sure it wasn't damaged while running dry. When you replace it (again), make absolutely sure you also replace whatever gasket or o-ring seals the cover as what you describe sounds suspiciously like an air leak - vane pumps such as these are self-priming unless there is an air leak someplace along with route from the thruhull to the pump.

 

[Rich Stidger]

If you replaced the original impeller because it failed and broke into pieces, be sure that you don't have a piece stuck into the outlet of the pump. It could block the water very effectively.

If you just replaced the impeller for preventive maintenance then there should be no pieces and then I agree that the issue would be an air leak as Don has suggested.

 

[Steve Dion]

Don:

Just start at the beginning. You may want to add some water to the sea strainer to get you going.

Close the seacock for the raw water intake. Remove the hose and see if you have any blockage (open/close) the seacock. The next spot is the the sea strainer..... You may have some critters that have taken up house keeping in the raw water side.

 

[Don Crowther]

Thanks for the replies

Another thing that I forgot to mention is when I replaced the hoses I used automotive heater hose. The new hose is more flexible than the ones I replaced. Is there any chance that this new hose is collapsing from the suction of the pump? Maybe I should use hyd. hose?

I didn't replace the impeller because when i inspected it I found no cracks and it was still very flexible. I was able to pull the impeller out with just my fingers so there shouldn't have been any damage. I didn't have a replacement gasket with me ( I had ordered the wrong part #) so I used some silicone around the old gasket when put it back together. Do you think that there's any chance that air could still be leaking by?

I think Steve has a point about checking the for blockages and will do that next weekend when I get back to the boat.

Not having a marina or parts source in town is a pita. Everything I do has to come by mailorder. Or you have to source out from other appilcations.

Don

 

[Warren Milberg]

It certainly sounds like your problem is that the raw water pump cover is not sealed properly with the correct gasket. You may want to open the pump again, carefully remove the sillicone you put on (remember that is really easy to nick the mating surfaces so be very careful), and then replace the cover on top of a proper gasket. I put a bit of liquid detergent on the gasket to hold it place while seating the cover. Also, remember to replace this gasket anytime you open the pump to either inspect or replace the impeller. If you buy them online/mailorder, buy a half dozen or more to make sure you have spares when you need them (impellers, too).

 

[Steve Dion]

Don:

On our H'31, I would get a piece of stiff wire and run in down the raw water intake. Obviously you need to remove the hose off the valve to do this.

As far as your hose is concerned, you want to be sure that is is reinforced and suitable for below the water line.

I would also check Warrens advice. Check out the lid on the sea strainer. It may be leaking which may cause your engine to not prime. I assume that you would see water leaking out of it if this were the case. That used to happen to ours if I did not seat everything properly.

Once you check out the intake, you should be able to remove the pump and cover and water should be flowing out of the raw water pump. Your hose will not be effected without the engine running.

Good luck and let us know your findings.

 

[Don Crowther]

Well I made it down the the marina this weekend. My parts ( imlpellers and gasket) didn't arrive in time. So I figured that I could still check out everything that you mentioned. First i pulled the hose off the seacock and made sure the water was flowing. Then I removed the hose off the strainer to make sure it was clear. I then took the strainer apart and made sure that it was sealed up tight.
It was then that I pulled the hose off the other side of the strainer and filled it with water.
I figured that since I had the pump apart last weekend it might not be primed. I was able to put about a pint of water in the hose to the pump. We then started the engine (yanmar 2gmf) And low and behold water started coming out and the pump worked fine.
Now that my parts have arrived I can change the impeller this weekend and put a new gasket on as well.
Thanks for all the advice as always it was great
Don

 

[Deadline]

1. Glad it runs with water coming out the back. It's almost impossible to find chunks of impeller in the lines. Blowing them out as you have by running the engine seems to have eliminated that problem.

2. Be very careful about replacing the gasket. On my 18 Yanmar 2GM I inadvertently added a gasket when all it needed was the O-ring. (Some pumps have no O-ring, thus a gasket is needed.) The effect was to create tiny air leak that compromised the vacuum and ran the engine dry. Boom! went the exhaust hose. It took me six weeks and an experienced Yanmar mechanic four hours to deduce the redundancy. It didn't present as an apparent leak of water because there was none.

 

[graham]

Just my $.02. If you have good coolant flow now I would leave it alone unless you suspect a fault. It's possible that (as with mine) the blockage was on the exhaust coolant inlet side, and that pressure and flow has cleared it.

If you replace the impeller now I'd order another as spares. You can always clear lines if a block happens, but if the impeller goes you'll be happy to have a second.