How not to check the water impeller for damage

[swillmerchant]

I'm glad to hear that your hard work paid off in the end. Thanks for sharing all of your experiences, good and bad. Your posts help me visualize what I'll probably experience once I tackle this on my own one day. I'm putting together a maintenance procedures binder for our tug based on all the great advice I've found on Tugnuts.

 

[baz]

So, from what I'm reading, running your Ranger in petroleum polluted water could shorten the impeller's service life?

One must assume so based on the warnings that are included with the new replacement impellers.

I would also suspect boaters who experience premature impeller failures fall into one or more of the following conditions

1) Run through dirty water
2) Run through water with fine sand particles suspended
3) Run to close to the sea bed for prolonged times
4) Have failed to open their thru hull valves too many times causing the impeller to run dry for short times
5) Run their engines at high RPMs for long periods of time exposing the impeller vanes to more stress/strain and many more impeller revolutions per mile compared to running longer time but at lower RPMs. I have to assume the raw water cooling impeller has an MTTF (mean time to failure) that is a function of the number of revolutions it makes before failing, ignoring all the other numbered items listed here.
6) Improper installation
7) Bad luck
8) Ingested small non-compressible objects through the hull's water scoop and passing through the raw water strainer such as pieces of wood and hardened plastic pieces.
9) Running boat through polluted waters with oil and petroleum based products suspended in the water.
10) Over the long haul the interior surface of the pump becomes grooved, pitted, scoured, rough etc placing undue stress on the impeller vanes

 

[knotflying]

Well Barry, I am glad you survived! My experience on the R-27 was nowhere near the nightmare you had. I am sure though that next time will be easier. I did enjoy the picture of your grandchildren in their new chairs.
Take care

Mike Rizzo

 

[walldog]

So, from what I'm reading, running your Ranger in petroleum polluted water could shorten the impeller's service life?

One must assume so based on the warnings that are included with the new replacement impellers.

I would also suspect boaters who experience premature impeller failures fall into one or more of the following conditions

1) Run through dirty water
2) Run through water with fine sand particles suspended
3) Run to close to the sea bed for prolonged times
4) Have failed to open their thru hull valves too many times causing the impeller to run dry for short times
5) Run their engines at high RPMs for long periods of time exposing the impeller vanes to more stress/strain and many more impeller revolutions per mile compared to running longer time but at lower RPMs. I have to assume the raw water cooling impeller has an MTTF (mean time to failure) that is a function of the number of revolutions it makes before failing, ignoring all the other numbered items listed here.
6) Improper installation
7) Bad luck
8) Ingested small non-compressible objects through the hull's water scoop and passing through the raw water strainer such as pieces of wood and hardened plastic pieces.
9) Running boat through polluted waters with oil and petroleum based products suspended in the water.
10) Over the long haul the interior surface of the pump becomes grooved, pitted, scoured, rough etc placing undue stress on the impeller vanes

If running through water with fine sand particles suspended and running close to the sea bed were a factor, I would certainly have a short MTTF, which I do not. I have a few hundred hours running in turbulent sandy waters ranging from 3 to 6 feet to a max of 16 feet without seeming to affect the longevity of my impeller.

I realize that I am only one data point, but I do run at high RPMs at great deal of the time. While I do like the economy of hull speed travel, sometimes you just have to get up and go. High speeds and shallow water are a way of life along the Texas Gulf Coast.

Most petroleum based pollutants and small pieces of wood and plastic float and therefore would not likely be entering the system through the water scoop placed a couple of feet below the surface. I do not think this is a factor in the failure of impellers. The small particles and sand should just pass through without appreciable damage to the impeller blades. I would think that the caking of salt from sea water drying out would be more of a factor. Although this too probably is minimal.

I think that your #4 is the only reason that either could have an appreciable effect on impeller life or is something we could control.

A factor you did not mention is shelf life. I would think that the older an unused impeller is, the shorter its useful life.

 

[baz]

Herb:

First, I'm no expert on impeller failure causes. I'm simply speculating what may cause premature failures based on some common sense and some structural engineering background.

I believe you mentioned a few weeks back that you would be entertaining replacing your impeller. When you do, could you take some photos of the impeller you remove and post them. I'm really quite interested in seeing the state of impellers that have been in boats for a considerable time without failures.

Yes the shelf life could also be a factor affecting MTTF. When storing them they should be kept in a cool, dry and shaded from daylight. This is per the details given with the new impeller packaging.

Looking at how much the impeller vane bends over at the smallest radius in the impeller housing leads me to think that high RPMs of the impeller (and hence high engine RPMs) will likely place a great deal of stress/strain close to the root of the vane (speculation on my part -- but a reasonable assumption IMO). A vane will be close to being bent over around 90º at around a point 1/3 of way from its root. I tried bending a vane in this way before placing it into the pump housing and it was not easy. The vanes are quite stiff and have the capability of springing back to their unbent position very quickly. I also suspect that over time they start losing this ability to spring back to their initial/original positions and hence lessen the overall effectiveness of the pump.

To me, the state/condition/wear of an engine and it's auxiliary equipment that's attach to it is more of a function of the total number of engine revolutions rather than an odometer reading (miles driven) or engine hours. It's a shame that total engine RPMs is not a number available when buying a used auto. 😉

The various impellers I've seen that are close to no longer performing at 100% are ones that have the beginnings of cracks just up from the vane root areas. This is the spot of maximum stress/strain when the vane gets bent over as I described above. I suspect these cracks are due to a phenomenon called fatigue which is normally associated with metals... but also affects non metal materials just as well... kind of like bending a small diameter wire back and forth until it simply breaks in two.

I will contact Lois and Dan Chaney (Hoku Kai - R-25SC, Olympia WA) who had their 250 hr engine service while at the Fisherman's Terminal meeting, and who had their impeller replaced at same time. I asked to see their old impeller. Three vanes were cracking/splitting equally at both ends and extended inwards by about 1/2". I believe the cracks/splits start in from the outer edge of the impeller because the friction on a vane as it rotates is on three sides; the long longitudinal edge and the two radial edges. Had Lois/Dan left their impeller in for much longer quite likely those vanes would have cracked/split 100% and pieces of them pushed along into the engine's inner raw water cooling system. What was weird was that the three cracked vanes were adjacent. This makes me wonder if their boat had been left unused for a fairly long period of time with those three vanes located at the smallest radius of the pump and hence left bent over at 90º for a considerable time. I will also ask them if they typically run at high engine RPMs. I have to say it was looking/examining the old impeller that came out of Hoku Kai that convinced me to replace my impeller as my engine hours were close to Hoku Kai's.

 

[walldog]

Unless it fails before...heaven forbid, I will be changing the impeller when we return to Anacortes later in the week. I will certainly take pictures and share them.

I note that the service tech said the next one he changes, he will remove the pump. I will also consider this method myself unless someone can give me reasons for not. I removed the pump to change the impeller on my 21 classic with 18 hp Yanmar. It had excellent access :mrgreen:

 

[baz]

Herb: If you or your engine technician removes the whole pump assembly please take notes and post back how well/easy this was. My Gallery Marine in Seattle engine technician yesterday also said they will sometimes remove the whole pump assembly as it makes it far easier to deinstall and reassemble the impeller and seat its end plate with O-ring precisely as well as securing the 4 hex head bolts. Also take note of how the impeller's pulley belt is removed and replaced via the 'walking' method cranking the engine manually and using the 22 mm center nut as Mike, Jim and I had to do.

Here's a snippet about impeller failures and do's and don'ts from West Marine... Ref http://www.westmarine.com/webapp/wc...51&page=Impeller-Replacement-101#.Ua-GDBa9P4M

When they fail
Flexible impeller pumps work best when run regularly. If your pump sits for months with the impeller in one position with the blades on one side bent, it may “take a set” and may blow a circuit breaker on startup (if it’s electrically driven). The impeller may also stick to the housing and come apart when the pump starts. Impellers are damaged by debris that get sucked in, by chemicals, and especially by running dry.

 

[baz]

Having gone through the complete impeller replacement on my MY2010 R-25 with Yanmar 4BY2-150 engine I'm now thinking about to make the access to the impeller assembly more accessible.

One thought is to modify the round floor hatch used for accessing fuel tank's shut off valve. There are larger oblong hatches available such as those installed on the R-27 I've seen. Maybe this type hatch will provide not only access to the fuel tank valve but also offer improved arm and visual access to the impeller assembly. I will be asking Andrew about this possible modification as the cabin floor has an inner honey comb structure and I would not want to compromise the structural integrity of the floor strength in that area. I will at times lurch or be lurched/thrown by boat movement into the cabin and land quite heavily on this floor area. :roll:

The alternative would have been for Ranger Tugs to make the step deeper and thus making the gap between the engine and the cabin step riser's floor lip further forward by say 2". This would make a huge difference in getting arms down to the lower section of the engine and could in fact allow two arms and the hands to join up to manipulate things such as the seating of the impeller's O-ring seal.

 

[walldog]

I am thinking....and I know that is dangerous, but. What constitutes "checking your impeller"? Very easy to check the condition of the belts. Yanmar's manual states that at 250 hours you check or replace belts and impeller. Does running the engine and looking at the exhaust water discharge suffice? I did my first 250 hour service, and I let an authorized Yanmar service facility do the 500 hours service. I did a much better job when I did it alone. A visual of the belts and verifying that the exhaust was discharging water was the extent of the check. The Yanmar manual lists things to be done at 1000 hours and 2000 hours. The impeller is not "scheduled" to be replaced until 2000 hours. My guess is that if you never run it dry either by forgetting to open the seacock or not cleaning trash out you probably should get that 2000 hours. I would imagine also that just a short time running dry would cause impeller failure or shorten the life of the impeller drastically.

What is the collective wisdom of this group? I know many have definite opinions...lets hear them.

 

[baz]

Please note that the P key on my daughter's laPtoP is inoPerative and I'm having to Paste in the P whenever I need to...

Here are my things to check for to give me a strong sense the imPeller is not or may be in need of being rePlaced

1) Sufficient water seen exiting the water exhaust Port... and this has to be based on a baseline when imPeller new.

2) Engine coolant temP holds steady at around 188 to 190 at low to high RPMs

3) No water leaking around the imPeller housing

4) Engine high temP alarm sounds and no water seen from the wet exhaust Port... Time to call BoatUS/Towing for helP

5) In my case at around 4 years and some 270 engine hours I observed no imPeller issues... it looked Pristine... so from this I would say at least check it every 4 years if engine hours above say 500 or even 1000 hrs without other issue as mentioned above.

6) RePlace Per the Yanmar maintencne schedule

7) RePlace if boat left out of water and engine not run for 1 year and if all raw water drained from the engine system. This would be because the 3 vanes bent over at 90 deg could be stuck and remain at this angle when imeller eventually rotated or worse still get stuck/glued to the inside of the Pums inner housing surface.

8) If you are convinced you've been boating in shallow and very sandy water for extended Peiods of time. The sand Particles will wear away the imPeller material as well as groove the imPeller housing inner surface. This could also mean rePlacing the whole PumP assembly.

9) RePlace imPeller simPly for Peace of mind. I did this recently because so many TugNuts were rePlacing their's and finding the imPeller was comPromised. Most recent was an R-25SC with 260 hrs and their imPeller had three vanes seriously cracked/sPlit 1/2" at each end

10) If you have time on your hands and any of the above items bother you and you want to drink several bottle of strong refreshment. Read Mike's osting for a suggestion. 😉

 

[walldog]

I am thinking....and I know that is dangerous, but. What constitutes "checking your impeller"? Very easy to check the condition of the belts. Yanmar's manual states that at 250 hours you check or replace belts and impeller. Does running the engine and looking at the exhaust water discharge suffice? I did my first 250 hour service, and I let an authorized Yanmar service facility do the 500 hours service. I did a much better job when I did it alone. A visual of the belts and verifying that the exhaust was discharging water was the extent of the check. The Yanmar manual lists things to be done at 1000 hours and 2000 hours. The impeller is not "scheduled" to be replaced until 2000 hours. My guess is that if you never run it dry either by forgetting to open the seacock or not cleaning trash out you probably should get that 2000 hours. I would imagine also that just a short time running dry would cause impeller failure or shorten the life of the impeller drastically.

What is the collective wisdom of this group? I know many have definite opinions...lets hear them.

I have answered my own question: At Two years and 630.1 hours, my impeller has three vanes that have definite although minor cracks. They were still functioning and I am sure that any reduction in efficiency of the pump was not noticeable. However, I am sure that there would have been total failure well before 8 years or 2000 hours. Probably would not have made it to the 750 hour service. I believe that based on this I will be changing the impeller at each 250 hour service or annually.

Does anyone know what the two rubber discs are that were both in one end of the new impeller shaft ?

 

[baz]

Herb: Glad you got to your compromised impeller before it failed and caused you more head aches etc.

It really is intriguing me that about all of the failing impellers I've seen recently ALL have THREE vanes cracking/splitting. When I inspected my impeller last week before I extracted it from its housing I noted that three of its vanes were bent over at 90º at the thinest vane dimension. This is where the housing radius is at its minimum. I wonder if this can be correlated with there being three vanes always cracked/split when people replace their impellers ?

In my case, no impeller vane was cracked/split, but three were permanently bent over more than the others.

Based on my boating I'll be replacing my impeller at 4 years or each 250 hrs of engine use, which ever occurs first.

Are you or have you replaced your impeller as a DIY task ? If not, I would strongly advise you make sure there are no leaks coming from the pump housing due to improper O-ring seating. At the Bremerton National Marina day I met up with an R-29 owner who had their impeller changed by a Seattle-based commercial engine servicer, only to find after that the housing leaked because the O-ring had not been seated correctly. Not sure how, but this owner ended up having to replace the whole pump assembly for a whopping $1700. He went to another engine servicer to have repairs made to get the issue resolved. This R-29 owner is still trying to get some kind of refund for the expensive mistake made by the presumably qualified Yanmar engine technician who installed the O-ring incorrectly.

You asked... "Does anyone know what the two rubber discs are that were both in one end of the new impeller shaft ?"

My replacement impeller had no such rubber disc plugs (if that's the right term to use). My only thought is that they might simply be plugs to protect the bronze shaft's inner surface from oxidizing or there to avoid crud/dirt from getting onto the bronze surfaces. What was the replacement impeller's brand ? Johnson Pump maybe ? Did you buy it from Ranger Tugs or elsewhere ? I cannot fathom what use the rubber discs could have. Maybe one uses them to extract the old impeller somehow... dunno.

Were the rubber discs the same material as the impeller vanes ? If so, maybe they were simply left over from the manufacturing process and have no purpose.

 

[walldog]

As we speak, the engine is running and making plenty of water. No leaks, but will check again when we get up to normal operating temp. I did the job myself, thanks to Mike, Baz, Richard, and others who have gone before me. I did the job completely from inside the cabin on the floor with my head and shoulders in the access hole. I could only get in so far as my chest is too thick. Not because of weight, but bone. If I can find another hatch about 1 inch taller, I will change it out. Not sure I want to go to the trouble of making a step. Besides I would be concerned about structure, as the door frame does a bit of twisting under stress as it is and cutting the molded step out would weaken that area more.

It is a one person job, Willie was very helpful to hand me tools and other supplies, but only one person at a time can get in that hole.

I won a parts kit at Bremerton last year and I bought an extra impeller from Ranger Tugs. I used the one in the plastic bag without any other supplies. It is identical to the factory unit. A Johnson 1023. The O ring looked good and remained in place. I did not change it.

It would be a much harder job to remove the pump assembly. Not an option for me.

The two rubber discs do not have a function...they could be left over from the manuf. process. I do not know they fit the hole perfectly so that is a possibility. I can imagine the packer at the plant thinking "I will just put these in the end to make the installer worry about what they are for."

Temperature is moving up so slowly that I will shut it down now to put the insulated panel and access door back on....its happy hour time.

 

[baz]

Well done, and be thankful the O-ring stayed put. I agree about the structural issue with making the step modification as I have the same concern with our R-25. In fact I don't believe it's possible on our R-25 as I discovered there's a support molding directly below the center of the step's riser and presumably it's there to provide stability to the floor flexing in that area. Mind you, I did post a topic about the door frame alignment which I resolved because the screw/bolt that secured the cabin wall to the inner wall was mispositioned and held absolutely nothing. Relocating this screw/bolt has completely resolved our door frame flexing issue and now secures the cabin wall correctly and securely, and the door latches with the slightest push now. 🙂

If my wife was present while I replaced our impeller she would have tried pulling my legs away to get out from that dam hole. As it was she was very alarmed at all my bumps and bruises and told me in no uncertain terms I was a silly man and that I could not use her makeup mirror for vieing stupidly located hidden bolts ever again. 😉 :lol: I found the job a real challenge but then I have always enjoyed doing something that seems to be impossible. :roll:

Did you wash down the impeller pump exterior area to avoid the leaked out salt water from causing long term rusting? This was advice given me by Jim.

I take it you also used the towel safety net for dropped items... I did and thank you for that tip as it saved me at least three times.

I would keep an eye on the coolant temp for several hours when you next take the boat for a ride, and vary the engine RPM up to 3500 for 10 mins to see if the temp rises more than 2 degrees from normal (for me, normal is 188ºF). Mine would rise to 190ºF and stay put there. I also checked the puller belt several times to make sure it had stayed in its grooves.

Don't throw away your old impeller as it might just be needed by you or some other TugNut friend nearby.

You deserved your Happy Hour... 🙂

BTW... what did Jake think about your head in the hole shenanigans ? :lol:

 

[Drifter]

Given the limited room on my vessel for essential maintenance on the Yanmar 4BY2-150, I confess to have been very apprehensive about tackling the impeller replacement. As there is no belt tension device I was rather daunted at the prospect of having to turn the engine by hand while easing off the drive belt. However, it had to be done so I set about the task and allocated a full day for the job.
Well, it was all done in less than an hour and I don't know why I was worried because it turned out to be one of the easiest maintenance tasks on the vessel. All you need is a 22mm socket for the crankshaft nut, a 6mm Alan key for the four pump end plate fasteners (behind the belt pulley) and some long nose pliers to pull the old impeller from the pump body.
The engine turned without having to use any extended leverage on my ratchet spanner and the drive belt ran off quite well by just easing it over the pulley with my fingers. The impeller was well lubed with washing up liquid and "turned in" without much of an effort and after bolting up the pump end plate, the belt was re-engaged by turning the engine while easing the belt back onto the pulleys.
I reckon you don't have to be a high profile spanner man to do this job so don't be frightened to give it a go.

 

[shellbacksailor]

In place of using Vaseline I used dielectric silicone grease on the o-ring and impellers that I changed each year on my old boat. My shoulders are too wide to fit through the access hatch on our new to us 25SC so I removed the hatch on the step front and cut up over and around a few inches in front of the door and back. This changed the front engine access from impossible to good... Not great as my old sailboats access spoiled me. I replaced the front and top of the step with starboard and used knurled bolts on the front for easy access to the fuel valve. I did have some worries about the door structural issues but I spent some of my misspent youth building fiberglass boats so I decided that access was the first priority for safety in the remote areas of the Sea of Cortez. I can use a piece of aluminum angle to stiffen the wood beam under the door if I see any flex at sea. You guys have a great forum here and have helped me tremendously, thanks, Micah.

 

[baz]

Micah: Photos ?

 

[tugnnaweigh]

I gotta say, for the time and labor to get to it; if I'm looking at my current impeller I'm pulling it and slipping in a new one. You also tend to be much better at it the second time!