Impeller mysteries ...

[Scott T-Bird]

The thread on the temperature alarm got a response from Benny which really rang a bell with me so, rather than hi-jacking the old thread, I thought I would start a new one.

I've always been wondering why my impellers fail and I can't find anything wrong with them. Benny suggested that oil in the water may cause separation between the hollow metal shaft and the rubber impeller so that the shaft spins and the vanes don't. I've thought about that in the past but I've never been able to actually see that it separates.

But I have noticed that I get an oily residue that accumulates underneath the cover plate of the impeller. I've had this for awhile and have replaced my injection line, and diesel fuel return line when thinking that I had leakage related to those components.

But I finally realized that water leaks from the cover plate of the impeller and I have recently tried to resolve that issue by replacing the gasket and the O-ring where the assembly gets put back together. I have even used teflon tape on the threads of the bolts that hold the whole thing together.

I've slowed the leakage but haven't been able to eliminate it. The water has an oily feel but it's a small amount that I just wipe up with a rag after operating the engine (which we never operate for more than an hour at a time on special occasions when I want to give it a workout).

I've noticed that the interior shaft (don't know what its called) is normally coated with engine oil, which I always assumed is normal. Could the engine oil be compromising the impeller and contaminating the raw water flow?

 

[Stu Jackson]

Scott, have you considered the design of the seals on the pump shaft? They keep water out of the engine and oil out of the pump. Perhaps your shaft seals are leaking.

 

[Bill Roosa]

Hey T-bird
I'm assuming your raw water pump is driven directly off the engine and not belt driven so if you have the belt driven type disregard.
The engine oil is used to lubricate the raw water impeller shaft. There is an oil seal (o-ring usually but not always) that keeps the oil inside the engine and away from the impeller. Sounds like you have an oil seal failure. That would explain the oil in the pump space. i have no idea why water would leak from the impeller cover. Almost sounds like the impeller shaft is not going all the way in and holding the cover off the pump body mating surface. Could be something on the shaft end (drive end not impeller) or something stuck in the hole that the drive end of the shaft slips into. Good luck inspecting the hole for an obstruction as it is not possible to get your eyeball in line with it. Try using a flash light and mirror.
for the record I'm still on my original impeller (since purchase) That is going on four years now. I do not pull the impeller during the winter but do loosen the cover and drain the water. And yes I have a spare. I had similar experiences with my other boats. Have not had to change on in going on 9 years now.

 

[Rich Stidger]

Scott,

A bit more info please. What brand of pump, what engine, and most importantly, what is the failure mode of your impellers? Does the hub separate, blades break or crack, or something else?

The pumps that I have worked on- various models of Johnson and Jabsco, have either a paper gasket (sometimes two in a sandwich) or an o-ring for the cover seal. But I have not seen a pump where the cover requires a gasket and an o-ring. Does yours?

If the shaft is not fully seated into the engine drive, then the impeller could be pushing out on the cover as Bill suggests. Maybe your pump requires two gaskets instead of just one?

 

[Scott T-Bird]

Worried now...

Stu, I hadn't thought about the possibility of raw water getting into the engine oil. I'm hoping that oil pressure has a tendancy to overcome the water pressure.

Bill & Rich, the engine is a Yanmar 1GM and it is driven directly off the engine. As far as I know, there is no separate pump make or model. Actually, I can't remove the cover plate without removing the entire housing for the impeller because the wheel for the alternator belt covers one of the screw heads of the cover plate and it seems impossible to remove the cover without removing the housing first. There are 3 small screws fastening the cover plate and 3 larger (9mm hex heads) bolts fastening the housing to the engine block. It is a simple matter to remove the hoses and remove the 3 bolts to pull the housing off and then replace the impeller (after removing the cover).

Actually, I've never seen any kind of oily residue inside the housing where the impeller fits. And, last summer I did replace the O-ring seal that fits between the housing and the engine block. I replaced it because of the oil and water that I noticed on the bottom of the engine compartment and I was surprised to see that the O-ring had been missing ... I remember finding an O-ring on the floor some time ago and I couldn't think of what it would be for ... I figured it out when I saw it had been missing. .

But here's the thing ... it seems to me that I am finding a small discharge of oily water from the bolts that hold the housing to the engine block. It seemed that one was discharging water so I wrapped it with teflon tape, which helped, but I still seem to get some wetness on the floor that I continue to mop up with a rag.

I don't think I have a problem with the cover plate fitting but I will consider it a little more carefully. If the housing isn't sitting properly to the shaft, I would think that I would see oil more so than water. I've never been able to figure out exactly what the impeller failures are. I can't see that the rubber separates from the hub and the vanes are always just as flexible and new looking as a new one. In fact I always have to be careful to keep the replacement impeller separated from the old one because they look exactly alike and if I put them side by side I would never be able to tell the difference.

 

[Ray Bowles]

Scott, On small plates that are bolted down on the corners it is not uncommon for the plate to become warped. If you have a good straight edge check the plate from corner to corned on the diagional. There are ways to overcome this warpage but the cheapest and fastest is a new cover. Second best is a piece of 600 grit wet/dry sandpaper and a flat piece of glass under it. You sand and sand until the plate is flat,
Just my 2bits, Ray

 

[Bill Roosa]

OK, I'm confused, you say the impeller fails but the vanes are all there and flexible and the rubber is attached to the shaft. What is left to fail?
The oily water that is seeping out the housing hold down bolt holes, is it raw water or anti? I would just taste it (and not swallow) but I'm hard as woodpecker lips, perhaps you could tell by smelling? The only place water and oil SHOULD come in close contact is across the oil seal on the shaft. A thought, the shaft may be lubed by water and the oil seal is on the drive that the shaft slides into.
This is the problem with internet troubleshooting.

 

[RichH]

If your impeller is an 'aftermarket' version of the OEM Yanmar impeller, these are very prone to failure of the shafting becoming loosened from the rubber vane body, etc.
If / when you replace, insist on an OEM Yanmar impeller, and not an 'aftermarket' impeller.

If you have oil inside the pump body (or cooling water draining into the crankcase), then you may have a leaking 'lip seal' on the shafting .... these are fairly easily to replace, but you need to set the 'clearances' of the lip seal to the pump body 'precisely' .. your 'tech manual' will have all the 'clearance specs.' etc. On most Yanmar pumps there should be a weephole that will drain to the 'outside' if leakage, in either direction, occurs ... if the weephole isnt blocked or 'painted over'.

 

[Stu Jackson]

Raw water pump seals

But I have noticed that I get an oily residue that accumulates underneath the cover plate of the impeller. I've had this for awhile and have replaced my injection line, and diesel fuel return line when thinking that I had leakage related to those components.

But I finally realized that water leaks from the cover plate of the impeller ...

Could the engine oil be compromising the impeller and contaminating the raw water flow?

Let's go back to the original question.

Scott, what do "replaced my injection line, and diesel fuel return line when thinking that I had leakage related to those components..." have to do with the impeller on your raw water pump?

I looked on marinedieseldirect.com for your Yanmar engine and they don't have any blow up diagrams of your raw water (cooling) pump, only a parts list. Hard to tell from that how it's built.

I agree it would be good to find out what pump you have and how it's built.

I agree with Bill and Rich. I also remember that Maine Sail did a great writeup on how to replace the seals, if indeed you have a raw water pump that is built the way Bill and Rich have described it, and how mine is, too.

Good luck. Keep us posted.

 

[joker460]

Here's the 1GM service manual. Maybe it helps.

https://docs.google.com/viewer?a=v&...jEtMmM5ZC00YmQ3LWIyYTUtNGQ1OTFjNDFlODE0&hl=en

 

[Don12364]

Scott,
By way of explanation, Yanmar raw water pumps have TWO lip seals on the drive shaft.
The one with the lip facing the impeller stops water running towards the engine and the second with the lip facing the engine stops oil running towards the impeller.

BETWEEN these two seals is a small air space which has a drain hole in the bottom to allow either water or oil to dribble out in the event of a failure of either seal.
Provided this hole is not blocked no cross contamination should occur. Your hole might even have been painted over! Try inserting a thin wire and wiggling it to make sure the hole is not blocked.

However, the oil and/or water you felt dribbling out of the pump could well have been coming from this hole.
Of course if the last person to remove the pump didn't refit the 'O' ring between pump body and engine block then oil would certainly leak from here too (but no water).

My guess is that there is no serious problem - however ANY leak indicates need for new seal(s).
Go to it.

 

[Maine Sail]

Scott,

The 1GM should have a belt driven RW pump not engine gear driven. If you have any oil inside the impeller pump body that would be very odd..

 

[WayneH]

OK, I'm confused, you say the impeller fails but the vanes are all there and flexible and the rubber is attached to the shaft. What is left to fail?

I've had a similar failure on a motorcycle. The starter motor would spin the motor with the spark plugs out but not when the spark plugs were installed. The starter idler gear is a one direction engaged set of gears that are press fitted. Turning it by hand felt like it was working correctly but installed it would not turn the motor. The press fit was failing but was still tight enough that you were fooled by it while turning by hand.

Take all of the above with a grain of salt as I don't own a 1GM motor AND I've never had my impeller apart. (yet)

 

[Maine Sail]

OK, I'm confused, you say the impeller fails but the vanes are all there and flexible and the rubber is attached to the shaft. What is left to fail?

Pump bodies wear, aftermarket impellers don't fit right, the wrong thickness gasket was used on the cover-plate, elbows get plugged, HX's get plugged, intakes get plugged, hose walls delaminate and collapse under suction. All of these can lead to what is perceived as an impellers failure to pump water..

 

[Bill Roosa]

So the failure is it don't pump for unknown non impeller rubber failure related problems.
OK, I got the impression he thought the oil was making the impeller rubber degrade in some fashion.

 

[Scott T-Bird]

Not belt driven as far as I can tell ...

MS, the body of the pump fits over a water pump shaft that disappears into the body of the engine block. According to my SELOC manual, the GM/HM series engines are belt-driven, but the 1GM is a different animal. Anyway, the only belt on my engine drives the alternator. I don't see any oil residue inside the impeller housing, only oily water residue on the floor of the engine compartment - and very little at that.

Donalex, the exploded view of the 1GM pump shows the 2 oil seals placed over the water pump shaft. I have to admit that I have never inspected that very carefully and I'll pay more attention. It seems that the shaft just kind of disappears into a tubular assembly inside the engine block. I'm wondering how I get access to those seals because I am thinking about replacement at this point. My fingers certainly won't squeeze into that shaft tube and I don't think a needle-nose pliers will get a grip either. Maybe some sort of pick ... I'll look for that hole ... It's funny that the exloded diagram for my water pump shows a paper gasket between the engine block and the water pump body. I remember being a little confused when the service desk at Lockwood (where I get my parts) gave me the o-ring when I asked for a gasket, but sure enough, the body had a little receptor groove for the 0-ring, so I put the question out of my mind (until now).

The Yanmar service manual seems to suggest replacement of the pump for these types of failures. I think I'll look into that. I don't have a problem with pulling the trigger for replacement parts to solve all kinds of aggrevating nuisances.

I can tell most of you have questions ... Stu, the diesel fuel return line and the pipe between the fuel pump and the fuel injector have nothing to do with this problem. The tiny amounts of fuel that was dripping from those sources were causing an oily residue to collect on the floor of the engine compartment at about the same location, and I remember thinking ... what the hell?!?! ... after fixing the one aggrevation and still finding an oily residue.

Bill, the failure of these impellers is stilll a mystery to me. In every instance where I replace an impeller, it is the impeller that fails, yet I can't see a reason why. I have even taken a failed impeller off and set it aside (until the next one fails) and then installed it once again to see if it will miraculously work. It didn't ... but after taking a new one out of the packaging and installing, the pump goes back to pumping water normally. Benny is the one who suggested that oil in the water could cause the rubber from slipping while the hub spins. I've not been able to verify this, but it sounds plausible. Anyway, he mentioned oil in the water in a different thread and it got me to thinking about the oily residue that I find on the floor of my engine compartment. There may be absolutely NO connection ... !

Thanks for all the comments! I think I might just replace the water pump and the oil seals. My baby is almost 30 years old and has been re-built before we owned her. But I think she responds well to new parts from time to time.

 

[Maine Sail]

MS, the body of the pump fits over a water pump shaft that disappears into the body of the engine block. According to my SELOC manual, the GM/HM series engines are belt-driven, but the 1GM is a different animal. Anyway, the only belt on my engine drives the alternator. I don't see any oil residue inside the impeller housing, only oily water residue on the floor of the engine compartment - and very little at that.

.

Yeah was thinking of the 2 & 3 GM's. The 1 GM has the triangular shaped cover plate IIRC. If it is one of those pumps there should be 2 seals, 2 ball bearing races and a couple of c-clips. They are easy to rebuild and very similar to a Johnson pump, in fact I suspect they are made by Johnson Pump for Yanmar just as they do for Westerbeke..

Rebuilding A Raw Water Pump

 

[Ron20324]

I don't see any oil residue inside the impeller housing, only oily water residue on the floor of the engine compartment - and very little at that.

If your marina is like mine, I wouldn't rule out that there may be oil in the water, and it all gets sucked into the impeller.

 

[Stu Jackson]

Scott, your choice is simple: either do a rebuild ala Maine Sail, or buy a new pump which will include the seals and maybe a carbon bushing (I didn't look at a picture of your pump). When we got our boat in '98 I noticed water weeping. I read Calder's manual. This was before all this great internet webbie tubie thingie, and found that having a shop redo the seals on my old pump would cost as much as a new pump. I bought the new pump. Now that I know more, I'd do it myself.

Ron makes a good point, but if your seals are going, you'd rather $$ on the pump than a new engine, right?

 

[Rich Stidger]

M In every instance where I replace an impeller, it is the impeller that fails, yet I can't see a reason why. I have even taken a failed impeller off and set it aside (until the next one fails) and then installed it once again to see if it will miraculously work. It didn't ... but after taking a new one out of the packaging and installing, the pump goes back to pumping water normally.

Scott,

I am still wondering about the impeller failures. You say that the pump stops pumping water and after replacing the impeller it is then fixed. You say that there is no visual defect of the old impeller but replacing it results in a non-pumping situation.

Have you held the center of the impeller and tried to turn the outside by hand? With no other change to the pump other than a new impeller, I fail to see how the fault could be anything else except the impeller, yet I don't understand why you cannot see or find an impeller fault.

An easy way to tell if the seals are leaking in the pump is to dry the exterior of the pump, run the engine, and then examine the pump exterior for any seepage. Be careful not to be fooled by condensation on the pump body due to cold seawater cooling the pump on a humid day as leakage.