Impeller Greasing in Engine Water Pump ?

[Shanaly]

hello, should i lubricate with lithium grease, soap, or....? i am starting up after a year+ of idleness and i want it to SPIN in < 20 seconds from engine start. i have also heard horror stories of impellers running dry for a period and melting so i was thinking of jetting water in, rather than rely on the engine/watter pump/impeller pulling water in from the thf
thsnkf
J

[sigmasailor]

It is wise to replace impellers regularly. If it has been standing still for a year now is a good time to replace it.
New impellers come with lubricant to avoid a dry start up the first time they are used.

[Hud3]

Put a little dishwashing detergent on the vanes before inserting it. Insoluable grease or lubricant in the fresh water cooling loop isn't a good idea, imho.

[moggie]

Next time you leave the boat, turn of the sea cock, open the water strainer, run the engine with fresh water (your shower) then give a good squirt of dishwashing liquid, before stopping the engine, now your salt water system is full of fresh water and you impeller will be fine. better still change it before you start the engine. They are cheap!!!

[Ziggy]

Do not put any petroleum based grease on the impeller. Either dishwashing detergent or silicon grease is OK.

[sailorboy1]

I think you probably are getting worried over nothing. Just start your engine and if the water flows great and you saved the time and trouble of taking the pump apart. If wrong you are just back to having to replace the impeller.

I think this impeller thing falls into the boater paranoid thinking where we worry big about small things.

[Seahunter]

Replace the impeller with a little Vaseline.

[Ziggy]

Originally Posted by Don Lucas

I think you probably are getting worried over nothing. Just start your engine and if the water flows great and you saved the time and trouble of taking the pump apart. If wrong you are just back to having to replace the impeller.

I think this impeller thing falls into the boater paranoid thinking where we worry big about small things.

This is a small thing that is worth worrying about. Impellers are a lot less expensive than new engines. On my Yanmar the impeller definitely needs a bit of silicone grease when starting after a layup to prime, and the new impellers come with a little packet of grease in the box for this purpose.

I replace the impeller every year.

[sailorboy1]

It's paranoid. If you allow an impeller problem to burn out your engine you weren't paying attention to start with. Replacing every year etc falls into "it makes the owner feel good" actions. I don't mind if you what to do but don't start making a big deal of it being some type of requirement.

On both of the Yanmar engines I've had that seawater pump has started right up just fine.

[bobconnie]

I was taught as a younger, to wash the raw water system down when a LONG lay up was nessasary. And I always put a fresh water hook up in to make this easy! to me a LONG lay up is 3 mos or more. different strokes as they say, but ive lost an impeller or two over 60 yrs of cruising, but never at start up. Bob and Connie

[Mike OReilly]

As someone who has suffered through an impeller destruction while running (and had to fish one of those little plastic arms out of the cooling system while rolling around), I would definitely recommend pulling it first. You many not need to replace it, but by removing it, you will ensure it isn't stuck to the housing wall.

If it's in good shape just re-insert with a little silicon grease. If it feels stiff, or worn, replace it. Impellers are cheap.

[s/v Jedi]

What you see in this photo is my new Northern Lights diesel genet. This nifty strainer is between the raw water pump and the heat exchanger. The screen is home made from a piece of thin wall 1.25" PVC pipe. The biggest holes in the screen are just a bit smaller than the channels in the heat exchanger.

If an impeller breaks up, the missing parts are either in the pump or it's outlet, in this strainer, or overboard with raw water discharge. No more need to remove heat exchanger to find missing pieces.

Remember that raw water plumbing on engines can sink the boat if a problem develops. This strainer is a weak point in that regard so check it often for leaks, weakness etc. The strainer on the photo is just my prototype version. I like it a lot though (tested it with an impeller already) and intend to make a Mk.1 version with a bronze housing.

ciao!
Nick.

[mbianka]

Originally Posted by Mike OReilly

As someone who has suffered through an impeller destruction while running (and had to fish one of those little plastic arms out of the cooling system while rolling around), I would definitely recommend pulling it first. You many not need to replace it, but by removing it, you will ensure it isn't stuck to the housing wall.

If it's in good shape just re-insert with a little silicon grease. If it feels stiff, or worn, replace it. Impellers are cheap.

I agree with Mike. I had a "yikes" moment back when I still had a diesel engine on board. Water was gushing out fine but, clearly the impeller was operating on borrowed time:
THE BIANKA LOG BLOG: Lessons learned: The raw water impeller.
Murphy was just waiting for the most inopertune time to make it fail completely. Solved all future impeller issues by converting to electric propulsion.

[Ziggy]

Originally Posted by Don Lucas

It's paranoid. If you allow an impeller problem to burn out your engine you weren't paying attention to start with. Replacing every year etc falls into "it makes the owner feel good" actions. I don't mind if you what to do but don't start making a big deal of it being some type of requirement.

On both of the Yanmar engines I've had that seawater pump has started right up just fine.

I am glad it's working out for you. But as they say, even paranoids can have enemies...

There there are a few reasons to feel paranoid about impellers:

1. A vane can break off, get sucked into the engine, and get lodged somewhere, like the heat exchanger, obstructing the water flow. You may get an advance warning of this if you see cracks in the rubber.
2. A common mode of failure is failure of the bond of the rubber body to the metal ferrule. When this happens the impeller still appears intact but does not function. This failure happens without any warning.
3. You are right to pay attention and frequently check for water coming out of the exhaust, but 1) inattention happens, and 2) even if you catch the lack of water in time, you will still have to stop and change the impeller (assuming you were at least sufficiently paranoid to carry a spare) or sail home. Depending on the conditions, it may not be that much fun. That's why many people spend a hundred bucks to replace their raw water pump cover with Speed Seal.

When starting up the engine with water drained out of the lines, the impeller turns dry without any lube. At least on some engines the pump may take a while to prime or it may not do so at all. During this time there is more wear on the rubber vanes than in normal use, and even if the impeller does not fail right then and there, the likelihood of a failure later increases. Putting a bit of detergent or silicon grease on the vanes doesn't take that much work and gives you practice in replacing it if you need to do so while under way.

Since the type 2 failure happens without warning, I replace the impeller every year, even though that is more frequently than recommended by Yanmar. I may be paranoid, but, again, even paranoids can have enemies and since I've experienced this type of failure twice before, I have adapted this practice on my boat.

[sailorboy1]

I carry a spare impeller and know how to replace it. I also have temperature indication and alarms. So I have 3 indications that are available before the engine is getting into an overheat (I also don't normally push my engine hard for long times)

When my boat is laid up that seawater pump is flushed with fresh water and then with glycol.

Did a poll once and it isn't common to replace requarly and the number of people who have had their seawater impeller fall apart were a lot fewer than what gets talked about.

Not saying there is anything wrong if someone whats to replace theirs every year.