MMI Impellers Shelf Life/ Pump Lubricant

[ArtJ]

How long can MMI Impellers be stored without degradation?

I typically have been changing impellers every two years, but always
keep a set of emergency spares for each pump,( salt and Fresh water pumps).
This means I am storing impellers for two years before installing,
then use them for two seasons.



Secondly, when I replaced the two impellers in my salt and fresh pumps
today, I put a layer of lubriplate (a white grease used on Seagull motors
in the past) I was going to use water proof wheel bearing grease, but
didn't have any on hand immediately.
Is the Lubriplate okay to use? Should I have used No grease?

Best Regards

Art

[Dave Neptune]

Art, I never change my impeller's unless I see a drop in flow!!! When I do see a drop in flow I have always been able to "get back" running easier if needed so she does not to heat up.

I always carry a spare and here is where I differ. If I ever had to replace one while out I have it for an emergency but it is a bit old, like the one being replaced. So when the flow slows and it's time to replace it I go get 2 new ones and throw the old unused spare away!!!!!! I then have a new impeller installed a newer spare and no worries.

They're cheap and I feel it is worth the loss of a few "liquid breads".

Dave Neptune

[ArtJ]

Thanks Dave
I was concerned with the blades becoming brittle and breaking off.
I have never had that happen, but used to change impellers every
season. Before I owned the boat, there were some pieces of blades
which I had to track down in the bends of the hose fittings.

Not sure I would know when the flow was less, unless it started
rising temperatures on gauges.

Best Regards

Art

[JOHN COOKSON]

I don't think you need grease.
Water or antifreeze is all that lubes the impeller when the engine is running.
I prime my impeller with water after I work on the H2O pump so it doesn't have a chance to run dry at the inital start up.
I keep 'em in a plastic bag so they are protected and don't get lost.

TRUE GRIT

[ArtJ]

THanks

I would like to know how long they will last unused (shelf life)
and in operation in either salt water or antifreeze.


Best

Art

[hanleyclifford]

Art - I would be cautious about using Lubriplate. IIRC it was what we used to coat the backing plate contact locations in the old drum brakes. Lubriplate is a lithium grease, I believe, which lithium is a positive valence earth salt which could be bad especially in a salt water pump.

[ArtJ]

Thanks Hanley,

I will try and wipe out .


Do you know how long the shelf life is for the rubber impellers before they
become brittle?


Best Regards

Art

BTW AMC has Jaws "Amity" on right now. Maybe I can see you on your boat?

[hanleyclifford]

Art - I don't know how long the MMI impeller would last on the shelf. It would matter how it is stored, but really how do you know how long it sat in the parts department before you got it? I get around the issue by having two MM 502 pumps which I change routinely. I also have a strainer in the antifreeze loop and no thermostat. All my fittings are of the plumbing type easy flow. So in effect I am counting on circulating and catching any escaping impeller fragments. Store your new impeller in a tight baggie in a cool dark place for best shot at longevity. FWIW Regards, Hanley

[ArtJ]

Thank you for the Insights .

Much appreciated


Art

[Ball Racing]

Yeah, my main thought is how long did sit on the shelf before you bought it?
Thats how long it was on the shelf at the place it was sold, how long did it stay in a warehouse from the main manufacture????

Do what lets you sleep good

[romantic comedy]

I bought several impellers from Don back in 1997. i still have them and they look good. Also I recently bought a blister pack that had a pump shoe and an impeller. That has to be 20 plus years old. That impeller was fine too.

here are a few, new and used

[ndutton]

I change the impeller annually. New one in the pump, the one removed from the pump in a baggie as a spare, the old spare in the trash. The routine keeps things pretty fresh.

As for mfr's and distributor's shelf time, why worry? You can't do a thing about it.

[marthur]

I think the answer to your original questions is a long time.

However, I do know that the aerospace industry standard for the shelf life for neoprene (which is what the MMI impeller is made of) is 15 years (ARP 5316). That is also the Mil-spec shelf life (Mil-HDBK-695D).

A lot of o-rings, gaskets and seals are made with Buna-n or nitrile rubber and the specs for shelf life for those is also 15 years. Most of the other polymers you might encounter (viton, silicone, hypalon, etc) have unlimited shelf lives in aerospace applications and a SHORTER shelf life than Neoprene in the Mil-spec.

Like some of the others, I switch my impellers out every couple of years or every couple of hundred hours of running. I usually have a new spare on hand, but I also keep several of the old impellers for spares but the oldest one is less than 10 years old and has less than 200 hours running. I store them in a sealed container out of the sunlight. Even though I can get CDO about reliability and maintenance some times I am comfortable that any of the spares would be usable in an emergency. (CDO is OCD with the letters in alphabetic order like they SHOULD be) I am sure that some of our fleet gets away with changing them less frequently but I do not want to risk an overheating situation in bad weather.

[ArtJ]

I wonder how long the impellers have been in place for the folks who
end up with failures - either broken blades or loss of suction?

I don't change impellers in my small outboards very often e.g. 5 or
more years at least due to the PITA of servicing the lower units.

Maybe they should be stamped with a "best by date" ?

[marthur]

I don't change impellers in my small outboards very often e.g. 5 or
more years at least due to the PITA of servicing the lower units.

I strongly suspect that it takes a very long for an impeller to die. I know many outboard motors that are running on impellers that older than I would ever rely on. I have even started some outboards up with 40+ year old impellers and they have held together long enough to test the motor.

That being said, I pulled impeller pieces out of my A-4 when doing routine maintenance a year or two after buying it. The PO (or the PO's PO--I am the third owner) had one go bad. That made me a believer in maintenance!

[marthur]

Looking at the bigger picture, we should also think about fuel pump diaphrams, bilge pump diaphrams and valves, o-rings and seals. Those will be made of very similar materials (or in some cases, the same material).

For those of us with a mechanical fuel pump, the diaphragm is worth replacing peroidically. When I rebuilt my fuel pump, the 30 year old diaphragm was looking cracked and worn out.

[thatch]

Over the years, I have had to play the "find the missing impeller blade" on quite a few occassions on other guy's boats. The broken vane is normally found lodged in the first tight elbow. I have a policy of inspecting my impellers on a fairly regular basis and, at the first sign of a crack at a vane's base, the impeller is replaced. I have a feeling that the quality of material used in our impellers varies from one maker to the next, so putting a "time life" number on them is difficult, if not impossible. I have some impellers that are well over 10 years old that are still working just fine, but I would consider them to be of "mil spec." quality.
Tom

[ndutton]

Tom,
You and I have discussed the perceived added stress on operational impellers with the M7 cam shoe upgrade. Could be a factor in useful life and/or maintenance routine.

[ArtJ]

Originally Posted by hanleyclifford

Art - I would be cautious about using Lubriplate. IIRC it was what we used to coat the backing plate contact locations in the old drum brakes. Lubriplate is a lithium grease, I believe, which lithium is a positive valence earth salt which could be bad especially in a salt water pump.

Just to double check , your experience certainly outweighs mine by far -
British Seagull used lubriplate to fill the lower unit of their outboard motors
which i believe were made of stainless gears with aluminum housing. I don't
think it did any damage in the 50 plus years they used it.
I was more concerned about the impeller and the O ring that is why I lubed
it with what I had on hand. The o ring will seep if no coating of grease
or petroleum. Link to lubriplate below.
https://www.google.com/url?sa=t&rct=...j5D9YXqK-EMIAQ

Best Regards

art

[hanleyclifford]

Originally Posted by ArtJ

Just to double check , your experience certainly outweighs mine by far -
British Seagull used lubriplate to fill the lower unit of their outboard motors
which i believe were made of stainless gears with aluminum housing. I don't
think it did any damage in the 50 plus years they used it.
I was more concerned about the impeller and the O ring that is why I lubed
it with what I had on hand. The o ring will seep if no coating of grease
or petroleum. Link to lubriplate below.
https://www.google.com/url?sa=t&rct=...j5D9YXqK-EMIAQ

Best Regards

art

Lubricating a sealed gearcase is one thing; running a lube around in a metal housing with salt water is another. No matter how volatile or dissimilar metals or compounds may be, unless an electrolyte is present no electrochemical reaction takes place.

[ArtJ]

What should i use to lubricate the o ring? If I don't they leak. Don
once recommended using vaseline ? to seal the oring on MMI pumps.
I will remove the grease

Thanks

Art

[hanleyclifford]

Originally Posted by ArtJ

What should i use to lubricate the o ring? If I don't they leak. Don
once recommended using vaseline ? to seal the oring on MMI pumps.
I will remove the grease

Thanks

Art

AFAIK Vaseline has no metallic component and is therefore a good choice.

[ArtJ]

thanks Hanley

[ArtJ]

Please excuse my question, but since the pumps are made of bronze
doesn't that mean the extra salinity caused will have no effect?

[hanleyclifford]

Originally Posted by ArtJ

Please excuse my question, but since the pumps are made of bronze
doesn't that mean the extra salinity caused will have no effect?

Many pumps run salt water with a bronze housing and stainless shaft with very little galvanic action because bronze and stainless are not too distant on the galvanic series. My point about the lithium was that since it is in the chamber and being thrashed around by the impeller and sent thru the engine it could pose a problem.