Impeller Key Out of Groove?

minuteman62-64 · Feb 15, 2013

1982 Mariner 30A. Replaced impeller a couple of months ago. About 3 hours on new impeller. Ran good at a steady 145 degree head temperature, good flow through tell-tale.

I run motor on muffs about once per month (maybe 15-20 minutes) just to make sure it is in running condition/ready to go. Last month I noticed it ran well at the start, then, when I was about to shut down, the tell-tale flow decreased and the head temperature increased to 180 degrees. I didn't think it was anything more than the hose supply pressure dropping, causing poor performance on the muffs.

This month I fired it up and there was no flow from the tell-tale. Started pulling things apart and squirting water in various locations. Flow through cooling circuits not a problem. Pulled the LU, removed the impeller housing and noticed the impeller was sliding on the shaft. Some rubber grains and smears in housing, but impeller still in good shape. I did notice the impeller fit very tightly in the housing.

I can reinstall the impeller with the key in the slot and it seems to work OK when I turn the drive shaft by hand. However, I'm concerned about how it came free.

Any ideas?

How can I determine if Crowley provided the correct diameter impeller? I can't find any specs.

Any ideas about what would make the impeller "jump" the shaft? Could it be too big in diameter so it turns too hard?

Texasmark · Feb 15, 2013

Re: Impeller Key Out of Groove?

The only way it could do that would be to have the ridge on the key worn down.....fat chance, or the top of the WP housing wasn't secured properly. However there are at least 4 screws and it is highly unlikely that if you had it operate properly for a time, that it would magically self destruct. The pressure in the water pump is developed by an eccentric housing about the drive shaft. The pump picks up water in a larger segment and as it turns the housing gets closer to the driveshaft which reduces the volume of the water and increases it's pressure in the process. So by it's nature it will fit tighter on one side than the other putting different pressures on the blades of the impeller.

Have no idea.

Mark

carholme · Feb 15, 2013

Re: Impeller Key Out of Groove?

What p/n impeller did you order from Crowley and what is your engine s/n?

Gerry

minuteman62-64 · Feb 15, 2013

Re: Impeller Key Out of Groove?

carholme said:
What p/n impeller did you order from Crowley and what is your engine s/n?

Gerry

S/n: 689407533.

Impeller part # (on Crowley diagram): 8479M

carholme · Feb 16, 2013

Re: Impeller Key Out of Groove?

That is the right p/n.

You say that the impeller was sliding on the shaft. Do you mean rotating because the key was not there and if so, where did you find the key?

I/m sure if you called Crowley they would measure the ID of a new impeller for you but why don't you just measure the OD of the shaft and the ID of the present impeller you have.

Is the key a good fit in the keyway as well as the slot in the impeller?

Gerry

minuteman62-64 · Feb 16, 2013

Re: Impeller Key Out of Groove?

With the key in the shaft, and mating with the slot in the impeller, I can hold the drive shaft stationary and rotate the impeller in either direction without too much effort. I didn't do that test when I installed the impeller, but I'm pretty sure the key was a good fit in the impeller slot at that time.

Here's a couple of photos. One shows the impeller top view, with the pump housing base in the background (showing rubber "smears." The other shows the impeller bottom view.

The impeller seems nice and rubbery, but, as you can see in the photos, there is some scuffing on the top and bottom surfaces and around the key slot.

Again point out - it's only a few months old with only about 3 hours use. I did use the factory service manual when I installed the impeller and gaskets, so I'm pretty sure I got the installation correct. And it did perform perfectly during the two hour sea trial and also on a couple of runs on the muffs.

carholme · Feb 16, 2013

Re: Impeller Key Out of Groove?

Kinda hard to assist if you don't answer the questions.

Again:

1. Do you mean rotating because the key was not there (when you took it apart) and if so, where did you find the key?

2. Is the key a good fit in the keyway as well as the slot in the impeller?

3. Why don't you just measure the OD of the shaft and the ID of the present impeller you have.

I am just trying to find out if someone installed the wrong key as it's purpose is to lock the impeller to the shaft. The key should be a good snug fit.

Gerry

Moody Blue · Feb 16, 2013

Re: Impeller Key Out of Groove?

minuteman62-64 said:
With the key in the shaft, and mating with the slot in the impeller, I can hold the drive shaft stationary and rotate the impeller in either direction without too much effort.

Rotate the impeller how much? There is a little play, but it should not be free to "rotate". When you say "without too much effort", are you turning the impeller OVER the key?

How about a picture of the key?

quicktach · Feb 16, 2013

Re: Impeller Key Out of Groove?

Try refitting the key and make sure it doesn't slide out when fitting the impeller on. I doubt if any things worn.

minuteman62-64 · Feb 16, 2013

Re: Impeller Key Out of Groove?

Moody Blue said:
Rotate the impeller how much? There is a little play, but it should not be free to "rotate". When you say "without too much effort", are you turning the impeller OVER the key?

How about a picture of the key?

Yes, the impeller turns over the key.

Picture of key attached.

I'm resigned that the impeller is shot. Just trying to figure out why so I don't keep chewing up impellers. Only thing I can think of is that, in spite of my care, it somehow ran dry when on the muffs.

minuteman62-64 · Feb 16, 2013

Re: Impeller Key Out of Groove?

OK, completed the last of my tests: with pump housing off, hooked up muffs and applied water pressure. Water flowed up through the slit in the pump base. So, clear flow path from water intake to pump housing and from pump outlet up through thermostat housing, through water passages and out exhaust port (with concurrent flow from tell-tale). To me that confirms that the impeller is the problem (or at least part of the problem).

Went ahead and ordered 2 new Sierra impellers from iboats (half the price of the Mercury ones - hope they work OK). Hoping the only issue was that I somehow carelessly let the impeller run dry.

minuteman62-64 · Feb 16, 2013

Re: Impeller Key Out of Groove?

And, one additional question. The key protrudes from the shaft 1/16 inch. Is that typical in a 30 HP? Does that provide enough purchase/grab to reliably turn the impeller (it's the same one that has been in there since 1982)?

Texasmark · Feb 16, 2013

Re: Impeller Key Out of Groove?

Just look at the alignment with the slot in the impeller after you slid it down in place over the key. You are metal on metal here. How does the interface look? Does it look like you have at least half of the two mating? Before it slipped, you'd see some vertical wear marks where it wore itself down till it did slip. Personally I have never heard of such a thing. Only way it might would be for you to have the wrong impeller dimensioned for a larger drive shaft...........but you already had that checked for you and it's apparently the correct one.

Mark

minuteman62-64 · Feb 16, 2013

Re: Impeller Key Out of Groove?

Texasmark said:
Just look at the alignment with the slot in the impeller after you slid it down in place over the key. You are metal on metal here. How does the interface look? Does it look like you have at least half of the two mating? Before it slipped, you'd see some vertical wear marks where it wore itself down till it did slip. Personally I have never heard of such a thing. Only way it might would be for you to have the wrong impeller dimensioned for a larger drive shaft...........but you already had that checked for you and it's apparently the correct one.

Mark

Actually, on my impeller it is all rubber. There is now metal "sleeve" that would provide metal to metal contact with the key.

It doesn't show up real well in the photos, but, there is some scuffing/wear in the impeller slot and on the inside of the impeller circumference.

When I get the new ones I'm going to make special note of the fit on the shaft and the security of the key/impeller connection - and make notes for future reference.

oldman570 · Feb 16, 2013

Re: Impeller Key Out of Groove?

I did noy see a brass inner sleve with the key slot in the old impeller. If this is the case, it could be that you did have it together correct. The tightness of the impeller when it was all put together might have held it from turning some an wore the inside of the rubber and let it slip and the key just hoged out the inside diameter of the impeller. If the thickness of the inpeller was just alittle more than what it should have been could add to the problem as when the top cup was put on it would pinch down on the impeller also. I have never seen a impeller that did not have the center brass keyed sleve and would never use a impeller that did not have one. The impeller should have a seal ring top and bottom close to the center to seal the top and bottom againest the cup and plate and from the looks of the plate on the LU housing shows that maybe the impeller was to thick. Any or all of these conditions could have caused the failure and shoud be taken into consideration. JMO
Oldman570

Mi duckdown · Feb 16, 2013

Re: Impeller Key Out of Groove?

micro the drive shaft OD than micro the impelar ID. see what you get. youd could have bought the wrong impellar

minuteman62-64 · Feb 16, 2013

Re: Impeller Key Out of Groove?

Neither the previous impeller nor the one shown in the photos (which is a Mercury part) have any metal insert/sleeve. I'll see how the Sierra ones are constructed when they arrive.

I'd feel a lot more secure if there were metal key slot in the impeller.

Texasmark · Feb 17, 2013

Re: Impeller Key Out of Groove?

There IS a bronze insert in the impeller. No way can you run that impeller on rubber drive alone. No brag just fact!!!!

Mark

Lone Duck · Feb 17, 2013

Re: Impeller Key Out of Groove?

texasmark said:
there is a bronze insert in the impeller. No way can you run that impeller on rubber drive alone. No brag just fact!!!!

Mark

yup!!

minuteman62-64 · Feb 17, 2013

Re: Impeller Key Out of Groove?

Son of a gun! Did some probing and what I thought was pure rubber isn't. It's not brass or bronze, but there is a hard insert - maybe nylon - in there.

I'll compare the Sierra ones with the Mercury/Mariner one as soon as they arrive. Maybe (hopefully) a better fit/more substantial key slot.

Impeller Key Out of Groove?

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