Need your experience

Nov 30, 2009
80
Oday 28 Lake Michigan
Fellow boaters,
I need feedback on an issue. I may have a issue with my marina launch procedure and need some of your experience. I'm asking this question very specifically as to not go off in different directions (which I typically enjoy, but do not want to do here.
I typically service my own water pump (replace my impeller). Real straight forward task. Typically when the water flow starts to show a weaken stream there will be a blade or two missing on the impeller.
Qestion: Have you ever shown a weaken stream of water and pulled the impeller to find not one or two blades missing, but EVERY blade missing? I just pulled my impeller and where there were 8 blades there was not a one. Completely stripped. Has this happened to you? Have you seen this?
 
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Nov 8, 2010
11,386
Beneteau First 36.7 & 260 Minneapolis MN & Bayfield WI
Changed dozens, seen that exactly ONCE. Pretty sure that instead of breaking and nicely exiting and ending up all by its self in the hose just before the heat exchanger, the broken blade jammed in the impeller housing and tore the others off as the hub continued to rotate.

PS - don't wait for that weakened stream and 1-blade failure to happen. Change every 1-2 years depending on hours.
 
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ToddS

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Sep 11, 2017
248
Beneteau 373 Cape Cod
I've never seen that, but frankly I'm kind of surprised I haven't. What Jackdaw said makes perfect sense to me... I could easily see one breaking off, and getting lodged "just right" in such a confined space, that it tore off all the rest. I know some antifreezes don't play nicely with some impeller materials (Ethylene vs Propylene Glycol vs nitrile or non-nitrile impellers) and conceivably you could simultaneously ruin/weaken/swell all the blades chemically, in the process of winterizing in colder climates, and then running the engine in springtime could rip all of the damaged blades off... that's just a thought though... never actually seen that or heard of that being a real problem. I probably just invented a problem that doesn't exist.
 
Jun 21, 2004
2,532
Beneteau 343 Slidell, LA
Think that Jackdaw is on to something here. Wonder if it's possible that installing the impeller incorrectly with the blades pointing in wrong direction could have contributed. I know for a fact that Yanmar recommends a specific impeller orientation for maximum pump efficiency....some mechanics have told me differently; however, I will subscribe to Yanmar's recommendations. Also running the pump dry with an inadvertent thru hull closed could have overheated the impellers resulting in a cascade of events as described by JD. Personally, I have never seen it happen. I don't accumulate a lot of hours on my engine; therefore, I usually change the impeller every two years; they always look new when I change them and keep it as a backup.
 

NYSail

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Jan 6, 2006
3,048
Beneteau 423 Mt. Sinai, NY
Good topic.... I started out changes my impeller every year for why not better safe than sorry, however never saw a broken blade and began accumulating a pile of used impellers. Now I do it every couple of years.... still have not seen any broken blades. I put on about 60 hours a year on engine I guess... I am going on year 3 with new boat (previous owner changed it year I bought her). Maybe I will change it this weekend.... still a powerful stream but why not.

Greg
 

cjm1

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Jul 10, 2013
40
custom Herreshoff 33 sloop Lake Charlevoix
I get years out of the raw water impeller on a Universal 5432. Every fall I loosen the plate to drain and before tightening in spring I put some Vaseline on the blades.to lube prior to start up. I believe all the impeller damage is done on startup before the water gets to the impellor.
 
Dec 29, 2008
805
Treworgy 65' LOA Custom Steel Pilothouse Staysail Ketch St. Croix, Virgin Islands
I've had an impeller with all the vanes off of it on our Westerbeke generator. Admittedly, it was after a few years of neglect! I believe it was just a matter of age. The important thing is to find ALL of the broken vanes before installing the new impeller. We found all of them, either in the exit from the pump, or jammed in the end of the heat exchanger. Of course, if you don't find them all, one will end up blocking the water flow somewhere.

To Greg's point above, if you do change every year, which is recommended but probably overkill (maybe every other year, depending on use), save at least the best of the used ones as a backup. We always have one new spare for each engine, but having a used spare is a good idea, especially if you go offshore.
 
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Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
Vaseline on the blades.to lube prior to start up. I believe all the impeller damage is done on startup before the water gets to the impellor.
I always hear impellers are dry until water is drawn up to the pump. Is there one engineer designer that would locate the pump below the water line so the pump is already wet?

Am I the only sailor who sees it this way?
 
Feb 10, 2004
3,917
Hunter 40.5 Warwick, RI
Unless there is an air leak in the pump circuit, there should always be water in the pump.
However I have a Volvo auxiliary where the pump is above the water line by about 18-24", and a Westerbeke generator whose pump is a good 36" higher than the water line. My service records for the last 22 years show that the auxiliary has had NO impeller failures, while the generator has had 14 failures. A failure is the loss of 1 or more blades.
So different pumps and impellers, but a dramatic difference in impeller failures. One generator failure was due to bearing failure and one was due to a severe seaweed plug. But the other failures were happened.
I suspect that the high generator failure rate is due to the higher lift and to the pump/impeller size. I have run the auxiliary DRY for 10 minutes by mistake and changed out the impeller, but saw no damage or stress cracks. So I think the auxiliary pump/impeller is more robust.
BTW, a broken vane or blade can get thrown into the intake port as well as the output port. If this happens, when the piece invariably gets free it will destroy the impeller. Always make sure you get all the pieces, or at least verify that there are none in the intake.
 
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Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
And if the hoses were clear you would know where those pieces went. OK, I’m done.
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
Even though both auxiliary and genset water pumps are below my boat's water line, that doesn't mean they are automatically "flooded".

I leave my thru hulls closed when leaving the boat.
I have my keys over the engine thru hull handle and a Caution tag over my genset start button, that reminds me to open them.
I "Bump" my engines to assure the impeller is free and lubed with water, before full start. I have a crew member verify I have exhaust water flow "immediately" or I will shut them down.

Tip: Remember when you change an impeller, put thin coat of vaseline on both sides. This gives reduced friction heat and allows water to fill the pump.
_____
Rubber impellers will deteriorate with time. Sounds like the PO lost one tip and then the domino effect.

Jim...
 
Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
Sailors lives have been subject to superstition and tradition for centuries, if I could explain. Jim and Brian I hope you don’t mind my using your quote, it sums up what is heard frequently.

Rubber impellers will deteriorate with time. Sounds like the PO lost one tip and then the domino effect.

Jim...
To Greg's point above, if you do change every year, which is recommended but probably overkill (maybe every other year, depending on use), save at least the best of the used ones as a backup. We always have one new spare for each engine, but having a used spare is a good idea, especially if you go offshore.
Now if rubber deteriorated with time, why save an old, used one for an emergency. In an emergency who wants bald tires when a brand new one is so cheap. Somebody must have researched this with proper data. I hope nobody risks ruining an engine having used an old impeller.

There are other options to cooling exhaust from boats.
 
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Jun 1, 2016
156
Hunter 28.5 Lake City, MN
It seems to me that someone told me that there is a replacement impeller that is made of a different and a much more sturdy material. (Lasts much longer.). I thought it was blue in color. Does anybody know what brand that was?

Mike
 
Feb 14, 2014
7,399
Hunter 430 Waveland, MS
A good description of "flex vane" impeller sea water pumps maintenance.
https://www.westmarine.com/WestAdvisor/Servicing-Your-Engines-Raw-Water-Pump

Nothing ruins a good cruise than loosing an engine when needed.:mad:

We engine travel to the Gulf on an major water run off river. The river water is never Caribbean or Rocky Mountain water clear. That means "deterioration" from just silty water extra friction.
_____
I thought it was blue in color.
Most are made from Neoprene rubber. The color at start is Tan, and they add Carbon Black to compound with it to be Black. If someone finds the newest one, let us all know.

Jim..
 
Dec 29, 2008
805
Treworgy 65' LOA Custom Steel Pilothouse Staysail Ketch St. Croix, Virgin Islands
Now if rubber deteriorated with time, why save an old, used one for an emergency. In an emergency who wants bald tires when a brand new one is so cheap. Somebody must have researched this with proper data. I hope nobody risks ruining an engine having used an old impeller.

There are other options to cooling exhaust from boats.
Maybe I should clarify my comment. Regardless of the material of the impeller (rubber or otherwise) I was referring to time of use, in the context of changing out impellers every year. I think one can actually expect to get more than one year of use out of an impeller, but I certainly don't dispute changing them out every year as recommended. However, to your point, sometimes a bald tire is better than a flat tire. and having a used spare is better than no spare at all. That's why I keep a spare used impeller in addition to at least one new one. Just in case. I've never had an occasion to actually use one, but if I needed another spare get home, I'd be glad I had one.

Could you elaborate on the other ways to cool your exhaust? While I don't think cooing the exhaust was the issue here, as opposed to cooling the engine itself (it didn't specify), I'd be interested in knowing other cooling strategies in an emergency.

While on the subject of emergencies, I've also considered the possibility of using the raw water intake to use as an emergency bilge pump. I'd prefer to use the generator raw water intake over the main engine, but either would provide some level of additional pumping capacity in an extreme emergency. Maybe I will start another thread on this subject so as not to hijack this one.
 

cjm1

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Jul 10, 2013
40
custom Herreshoff 33 sloop Lake Charlevoix
Another thought to alternative cooling. I have engine block heater in the cabin with engine coolant diverted via a Y valve. I would suspect with a full blower you could get emergency cooling. It sure move some heat when needed in cool fall sailing.
 
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Oct 2, 2008
3,807
Pearson/ 530 Strafford, NH
Years ago we docked by a steel bottom boat from Belgium. The boat was near 50 feet with zero thru hulls or seacocks and on their third trans Atlantic voyage. Our boat has 18 seacocks and many thru hulls near water line. Since then I’ve looked at a lot of boats.

I’ll start you off with one boat using a 12V pump for pumping raw water. List your objections along with a solution.

Do you need water to vent exhaust? Again objections with a solution.