Impeller Key Out of Groove?

[quicktach]

Re: Impeller Key Out of Groove?

You should have a brass or alloy sleeve as part of the impeller. The sleeve will have a slot machined into it. The hump on the shaft key will fit into the slot. There should be no sloppiness or play when you slide the impeller down over the key. A snug fit. Make sure you get the blades of the impeller in the opposite direction to the shaft rotation. The impeller inside it's casing operates as a centrifugal pump; so the blades must be in correctly. There should be a deep enough slot machined into the drive shaft to keep the key seated into the slot.

 

[Texasmark]

Re: Impeller Key Out of Groove?

Possible that an after market mfgr. could have substituted plastic (nylon) for bronze/brass beins the metal is getting (has gotten) quite expensive. Have no experience with such so I have no idea as to longevity.

On any protrusion of the key over the top of the impeller, I never saw such. Another possible indication of the wrong impeller. Really it can't and function properly. The impeller seals itself against the water pump housing. That is apparent by the groves impellers make in the top and bottom of WPs. If the key protrudes above the impeller and the WP cover fits over the two properly, it says right off that the impeller is not contacting one side of the pump housing and thus cannot produce a displacement pumping action to develop adequate pressure and force water thru the powerhead.

Mark

 

[minuteman62-64]

Re: Impeller Key Out of Groove?

Possible that an after market mfgr. could have substituted plastic (nylon) for bronze/brass beins the metal is getting (has gotten) quite expensive. Have no experience with such so I have no idea as to longevity.

On any protrusion of the key over the top of the impeller, I never saw such. Another possible indication of the wrong impeller. Really it can't and function properly. The impeller seals itself against the water pump housing. That is apparent by the groves impellers make in the top and bottom of WPs. If the key protrudes above the impeller and the WP cover fits over the two properly, it says right off that the impeller is not contacting one side of the pump housing and thus cannot produce a displacement pumping action to develop adequate pressure and force water thru the powerhead.

Mark

The impeller is a Mercury part #, but might well be a third party mfg. I noticed the new drive shaft seals I purchased at the same time had nylon rings instead of SS as the originals had.

To clarify, my observation of the key being out of the groove did not refer to the vertical position. The impeller was flat against the base and totally covered the key. The issue was the key being at 12 o'clock and the slot being at 3 o'clock (and relatively easy to rotate back and forth). I now wish I'd paid more attention to the impeller that was replaced.

The new Sierra impellers have been shipped so I'll probably get them this week. I'll be doing a side-by-side comparison before any re-assembly.

 

[Lone Duck]

Re: Impeller Key Out of Groove?

You know. I think that either some one has put the wrong part in the right box, or it is just a poorly made copy of the right one. Made in china ??

 

[minuteman62-64]

Re: Impeller Key Out of Groove?

OK, got my new impellers from iboats (pretty fast service - ordered on Saturday, arrived following Wednesday). I don't know what the tolerences on these things, but I compared some measurements. The new ones also appear to have some sort of nylon inserts that bear on the shaft.

Kind of difficult to measure the ID of the impellers, plus the old one was a little scuffed up/distorted. Anyways, the new one actually measured 1/128 inch greater ID than the old one - and 1/128 inch greater than the shaft diameter. It slides easily down the shaft. I vaguely remember the old one being a tighter fit on the shaft - but can't remember for sure.

Height of the impellers was a little easier to measure. Th new one was 1/64 inch lower in height. Should be a little less squeeze in the housing, but not sure how much difference it will actually make.

Biggest difference is that the new one locks solidly in the key - I can't rotate it against the shaft/key like I can with the old one.

Not sure if any of this is significant. But, I'll install the new impeller and see how it goes.

I'm still thinking I somehow ran the pump dry and chewed up the old impeller.

 

[CharlieB]

Re: Impeller Key Out of Groove?

Carefully scrape clean the inside of the OLD impeller.

You may find that the solid 'ring' of the hub has cracked, which allows it to 'spring' open enough for the key to slip and let the impeller to turn.

It happens, but not very often.

If you got the old impeller from a dealer, call them, see if they will replace it.

From the condition of the side rings and the tips, it was not run without water, no heating or melting at he major contact areas.

 

[minuteman62-64]

Re: Impeller Key Out of Groove?

Carefully scrape clean the inside of the OLD impeller.

You may find that the solid 'ring' of the hub has cracked, which allows it to 'spring' open enough for the key to slip and let the impeller to turn.

It happens, but not very often.


If you got the old impeller from a dealer, call them, see if they will replace it.

From the condition of the side rings and the tips, it was not run without water, no heating or melting at he major contact areas.

Bingo!

See attched photo. Just to the left of the key groove you can see a thin line that is actually a break in the nylon impeller "core."

I don't know if it came to me with a flaw or if I did it during assembly - but it sure allows the impeller to slip on the shaft.

 

[minuteman62-64]

Re: Impeller Key Out of Groove?

OK, installed new Sierra impeller, re-assembled and ran on the muffs. Everything seems good. Need to get out for a sea run and put a few hous on the new impeller to make sure. I'll be interested to find out if I just got a flawed Mercury impeller of if I have (or have created with my installation) a motor that simply eats impellers.

 

[gurugod1]

Re: Impeller Key Out of Groove?

Had the same sort of issue just recently with my 1989 30 hp mariner impeller. To the best of my knowledge, my woodruff key got a little cockeyed during installation or was too large top to bottom, allowing for too much contact with base plate. Caused impeller to fail and upon further inspection I found a rather deep groove in the base plate. This metal on metal contact melted the inside of the impeller and the housing above the insert cup. The shaft was spinning around the inside of the impeller after the impeller was stripped, causing a plastic and rubber mess. Was tough to pinpoint how that happened, but I thought about the possibility of wrong parts from Sierra, the same impeller you purchased.

Turns out that the key being slightly out of place after sliding on impeller actually bent the wear plate after firing up the motor and using it for a few hours, so maybe you want to check that out if you still happen to have issues with your impeller. In the future, I think I'll try to grind part of the key to avoid any contact with the base plate, allowing for the wp to work without any inadvertent heat oe friction issues after installation. Anybody ever heard of this issue before or know how to remedy?

 

[minuteman62-64]

Re: Impeller Key Out of Groove?

In my case I've concluded it was either a flawed impeller or that I somehow damaged it during assembly. The new, Sierra impeller has ben in for a number of hours now, still going strong.