Reply
 
Thread Tools Display Modes
 
Old 01-30-2015, 04:32 PM   #1
Guru
 
angus99's Avatar
 
City: Signal Mtn., TN
Country: US
Vessel Name: Stella Maris
Vessel Model: Defever 44
Join Date: Feb 2012
Posts: 1,386
Impeller Best Practices

Thought this deserved a separate discussion vs piggybacking on the "Stuck Impeller" thread.

Also, because these two impellers were easy to pull.

They are from the twin Lehman 135's on our Defever 44 and I discovered them this way after a 1,000-mile delivery trip from Florida to the head of the Chesapeake. I think there were 6 intact vanes on one and 5 on the other!



After seeing this and almost stroking out, I started collecting the bits of what I assume is neoprene downstream in the raw water system. You can see the debris from one of the damaged impellers below, alongside an intact impeller.



I learned a few things:

First, the Ford Lehman 135 must be one tough engine. Both engines were monitored routinely throughout the trip by a highly respected delivery skipper--via the temp gauges and regular direct infrared thermometer readings--and they never overheated. The exhausts were also checked hourly and no reductions in water flow were discernible. This was especially surprising after I found most of the neoprene pieces up against the tube bundles in the heat exchangers.

Secondly, I will never start a long cruise without new, or lightly used, impellers. The ones that came with the boat were likely rotated in and out of use to extend their service life.

Third, I'll probably chuck out impellers I replace even if they're intact rather than try to eek a few more months out of them. (I have already pulled them while the boat's laid up for the winter.)

Lastly, I'll check the impellers physically before, during and after trips. It was my bad that I assumed they were up to the trip . The new Speed Seal covers I just installed on the impeller housings should make that less of a chore.

If anybody has a better approach to impeller health, please share.

Better lucky than smart, I guess.
__________________
Advertisement

angus99 is offline   Reply With Quote
Old 01-30-2015, 06:28 PM   #2
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
I've seen this countless times. Few blades left on an impeller and the engine doesn't even run warm at cruise rpm. Each time it confirms two things to for me, 1 the "Lehman's are prone to over heating" statement I hear from time to time is an urban myth. And #2, it's good to run your engine up towards full rpm once in a while and leave it there for a few minutes or so to see if the temps climb indicating a possible water flow issue.
__________________

Capt.Bill11 is offline   Reply With Quote
Old 01-30-2015, 09:32 PM   #3
Guru
 
kchace's Avatar
 
City: Brookline, NH
Country: USA
Vessel Name: Blue Heaven
Vessel Model: Albin 43 classic double cabin, twin 135 Lehmans
Join Date: Sep 2013
Posts: 761
I think checking impellers before every trip to be a bit extreme - especially considering how many other items could also bring one's trip to a quick stop. For example, how are the many hoses and clamps on the engines? How about the oil cooler hoses? Most owners don't touch these but they all have definite lives and a failure in any one could cause serious problems and/or engine damage quickly.

I think if one has "recent" impellers that have not be on the shelf for years, and some spares, you should be able to expect at east a couple hundred hours from them (and often much more). Impellers don't usually fail catastrophically and a yearly change is usually sufficient for most types of use.

Fortunately, the impeller "bits" are an irregular shape and so won't easily block the flow into a tube. Still, it IS amazing that those impellers were as bad as that and the engines operated normally.

I think the advice about bringing the engines up to full power occasionally is a good tip. My situation is a perfect example. I had one engine that would always run 10 degrees hotter than normal if pushed above 2000 rpms where the other did not. This winter I have completely gone through the cooling system and found the main engine heat exchanger on that side defectively built! These engines have 2 pass exchangers. At one end is a "separator" plate which forces the water to go up half the bundle one way and come back in the other half. Well on this particular heat exchanger that plate had NEVER been soldered to the sides OR the end plate that holds the tubes. This left about a 1/8" gap which I calculated at 7" long. Some of the raw water flow in/out could simply shortcut the path completely and not go down ANY of the tubes. I calculated that approximately 20% of the raw water flow would simply bypass through the exchanger and not provide ANY cooling. The amazing part is that this exchanger had been in the boat at least 9 years and the engine never overheated. But the clue was how it always heated up a bit at higher rpm as opposed to the other one. Considering its age, I replaced that exchanger with a new one and will keep it as a "get home" spare.

Ken
kchace is offline   Reply With Quote
Old 01-31-2015, 07:59 AM   #4
Senior Member
 
waddenkruiser's Avatar
 
City: Southern Baltic
Country: Europe
Vessel Name: SÝmarken
Vessel Model: AMS 40'
Join Date: Jul 2012
Posts: 183
We change impellers yearly during our spring routine maintenance work. So they run ~ 200 h. We don't reinstall them regardless whether they look o.k. or not.



best regards / med venlig hilsen
wadden
__________________
best regards / med venlig hilsen
Wadden
waddenkruiser is offline   Reply With Quote
Old 01-31-2015, 08:00 AM   #5
FF
Guru
 
FF's Avatar
 
Join Date: Oct 2007
Posts: 16,531
MY solution has been to install Y strainers in line after the impeller pump.

This will catch all pieces and not restrict the water flow.

It is also quick to check if you think the sea cock or intake strainer is plugged.

Sendure makes excellent bronze units.
FF is offline   Reply With Quote
Old 01-31-2015, 08:03 AM   #6
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
My guess is much impeller damage is caused by sitting....and dry starts.

I get easily 4 to 8 hundred hours out of my and assistance boat impellers..even in incredibly sandy conditions on the tow boat.

That's based on around 400 to 500 hrs per year...the impellers look great and are pumping with no temp issues.
psneeld is offline   Reply With Quote
Old 01-31-2015, 08:19 AM   #7
Guru
 
City: Full Time Cruising East Coast
Country: USA
Vessel Name: Meridian
Vessel Model: Krogen-42
Join Date: Aug 2011
Posts: 756
My FL120 shut down last week on my way to the Bimini. 100% blockage of the strainer. The impeller was not damaged and looked fine after 1,100 hours.
__________________
-------------------------
Terry
Meridian
KK-42097
meridian is offline   Reply With Quote
Old 01-31-2015, 08:28 AM   #8
Guru
 
Capt.Bill11's Avatar
 
City: Sarasota/Ft. Lauderdale
Country: USA
Join Date: Apr 2014
Posts: 5,422
Just out of curiosity what blocked your strainer so completely?
Capt.Bill11 is offline   Reply With Quote
Old 01-31-2015, 08:39 AM   #9
TF Site Team
 
Larry M's Avatar
 
City: JAX, FL
Country: USA
Vessel Name: Hobo
Vessel Model: Krogen 42-120
Join Date: Nov 2008
Posts: 5,745
Quote:
Originally Posted by waddenkruiser View Post
We change impellers yearly during our spring routine maintenance work. So they run ~ 200 h. We don't reinstall them regardless whether they look o.k. or not. best regards / med venlig hilsen wadden
We also change/replace annually, on our schedule.
Larry M is offline   Reply With Quote
Old 01-31-2015, 09:06 AM   #10
Guru
 
City: Full Time Cruising East Coast
Country: USA
Vessel Name: Meridian
Vessel Model: Krogen-42
Join Date: Aug 2011
Posts: 756
We had gone through a large patch of fine sea grass. The strainer was full and the seacock was jammed with grass. It took a good but of time to clear all the blockage. It didn't leave us enough time to get to Bimini before sunset do we came back to Miami.
__________________
-------------------------
Terry
Meridian
KK-42097
meridian is offline   Reply With Quote
Old 01-31-2015, 01:19 PM   #11
Guru
 
Ski in NC's Avatar
 
City: Wilmington, NC
Country: USA
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 3,889
I've been in the marine engine business for almost 20yrs. I understand just about everything about these beasts- except trying to understand impeller life. I have seen impellers at least 10yrs old with lots of sitting time- look perfect. I have seen others coming apart after 100hrs with very little sitting time.

A few patterns are noted: The Jabsco's on Detroits seem to last forever. Sherwood impellers on Cummins don't. Mine included. Not only is the pump arguably a POS, but the impeller on mine likes to load the aftercooler with vanes even with little sitting time.

Mine can go 200hrs, I change the AC zinc and there are vanes. Hmm, where did they come from??!! Change impeller, yep in rough shape. Go another 200hrs, no vanes in AC. Go another 200, no vanes, ok. Get ready for long trip, put new impeller in just to be sure. Old one has 400hrs, looks great. Go on trip, put about 200hrs on new imp, change zinc on AC. Vanes in there. Great. 200hr imp coming apart!! Get p'd, put the 400hr imp back in. I think I have put another 400 on it, so now about 800 total. Checked aftercooler, no vanes.

Getting ready for another trip. So roll the dice and run on the 800hr one, or roll the dice and put a new but iffy one in???

These are all new impellers in factory Sherwood packing, bought from same vendor.

Go figure.

They last forever until they don't.
Ski in NC is offline   Reply With Quote
Old 01-31-2015, 01:30 PM   #12
Guru
 
Join Date: Apr 2014
Posts: 1,291
My experience from the east coast where there is shallow water and sand is that some boats and how they are used will suck sand and destroy impellers in no time. Here in the NW impellers seem to last a lot longer. One grounding or near grounding in sand with motor use to get off and its time to check your impeller.
eyschulman is offline   Reply With Quote
Old 01-31-2015, 03:10 PM   #13
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
Not sure sand destroys them...though it wears wear plates and pump bodies.

I probably put 50 hrs a year 2 feet of sand slurry as I pull boats off of sand bars.

I still get 500 to 1000 hrs on impellers.....sometimes more.

Once I wore a hole in the pump body and ran around for several days that way till it was located and a new pump put on.

I guess I have to agree with Ski more than anything.....no rhyme or reason why some impellers or pumps just don't last.
psneeld is offline   Reply With Quote
Old 01-31-2015, 05:13 PM   #14
Guru
 
LarryM's Avatar
 
City: League City, TX
Country: USA
Vessel Name: Pelago
Vessel Model: Wellcraft 3300 Coastal
Join Date: Aug 2011
Posts: 843
I found some interesting information in my shop manual for the Yanmar 4JH3E which uses a Johnson pump. The owner's manual calls for impeller inspection annually or 600 hours. The repair manual pump specifications indicate the design durability for the impeller is 1500hr minimum. I replace annually and do not re-use the old impellers. I keep one backup aboard and use it for the replacement so that the backup is always relatively fresh.

Johnson now uses "a new impeller compound MC97 which has also resulted in an extended service life of the impeller compared to impellers in Neoprene." Nitryl is only recommended where the pump will encounter oil.

FWIW, many Johnson impellers have Jabsco equivalents so there might be some interchangeability with other pumps and engines. I have heard some mechanics state that Johnson impellers are more durable, but that is only here say.
Attached Thumbnails
Click image for larger version

Name:	129670-42512Y Water Pump Specs.JPG
Views:	91
Size:	81.4 KB
ID:	37000  
__________________
Larry
M/V Pelago
LarryM is online now   Reply With Quote
Old 01-31-2015, 05:33 PM   #15
Guru
 
City: Hotel, CA
Country: Fried
Join Date: Sep 2011
Posts: 8,328
Quote:
Originally Posted by psneeld View Post
I probably put 50 hrs a year 2 feet of sand slurry as I pull boats off of sand bars.

I still get 500 to 1000 hrs on impellers.....sometimes more.
You've said before the assistance boat is powered by a 454 gasser. Out of curiosity which pump and impeller do you run on that boat? I have a Jabsco on my 350.
__________________
Craig

It's easier to fool people than to convince them that they've been fooled - Mark Twain
CPseudonym is offline   Reply With Quote
Old 01-31-2015, 05:33 PM   #16
TF Site Team
 
FlyWright's Avatar
 
City: California Delta and SF Bay
Country: Sacramento, CA, USA (boat in Vallejo)
Vessel Name: FlyWright
Vessel Model: Marshall Californian 34 LRC
Join Date: Apr 2008
Posts: 10,189
That's interesting, Larry. I switched from neoprene to nitrile 300 hrs ago. I used to change theneoprene then nitrile impellers every 200 hrs, but went longer this last time b/c the nitrile still looked like new on the last 2 changes. This time at 300 hrs, my impellers still worked and looked great, but I still replaced them.

I just looked at what I put in my pumps this week. I learned that I messed up and bought the neoprene impellers by mistake. They're already in there so they can stay for the next 200 hrs, then I'll replace them with nitrile impellers for the next 300 hrs.

Now that I have SS knurled head allen screws in the pump plates instead of the standard screwdriver screws, the job is much easier. I can now replace both impellers in about a half hour if I don't remove the salon carpet and hatches. That's a huge improvement over my previous experiences.
__________________
Al

Custom Google Trawler Forum Search
FlyWright is online now   Reply With Quote
Old 01-31-2015, 07:18 PM   #17
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
Quote:
Originally Posted by CPseudonym View Post
You've said before the assistance boat is powered by a 454 gasser. Out of curiosity which pump and impeller do you run on that boat? I have a Jabsco on my 350.
Not quite sure...in FL instead of near my boat ....thankfully!!!!!!!! !

Pretty sure it is a typical Jabsco that bolts to the front of the crankshaft...nothing unusual about it.

just another example that there are too many worriers on the forum that need more practical experience.
psneeld is offline   Reply With Quote
Old 01-31-2015, 07:48 PM   #18
Guru
 
angus99's Avatar
 
City: Signal Mtn., TN
Country: US
Vessel Name: Stella Maris
Vessel Model: Defever 44
Join Date: Feb 2012
Posts: 1,386
Quote:
Originally Posted by psneeld View Post
just another example that there are too many worriers on the forum that need more practical experience.
Until some of us attain your level of experience, is it still OK to ask questions?
angus99 is offline   Reply With Quote
Old 01-31-2015, 07:57 PM   #19
Guru
 
psneeld's Avatar
 
City: Avalon, NJ
Country: USA
Vessel Name: Freedom
Vessel Model: Albin 40
Join Date: Oct 2011
Posts: 15,920
Quote:
Originally Posted by angus99 View Post
Until some of us attain your level of experience, is it still OK to ask questions?
Asking is fine...even my experience is limited compared to guys like Ski and some others..

People post what they feel comfortable with and that's OK too.....but some think that a few hundred hours a year on one or two boats is a "range" of experience....not!
psneeld is offline   Reply With Quote
Old 01-31-2015, 08:26 PM   #20
TF Site Team
 
FlyWright's Avatar
 
City: California Delta and SF Bay
Country: Sacramento, CA, USA (boat in Vallejo)
Vessel Name: FlyWright
Vessel Model: Marshall Californian 34 LRC
Join Date: Apr 2008
Posts: 10,189
Quote:
Originally Posted by angus99 View Post
Until some of us attain your level of experience, is it still OK to ask questions?
Many of us have less experience than some and some of us sound like we have all the answers when we don't.

I come to this forum for different perspectives on solving a problem:

1. Sound advice from those with much more experience than I have

2. Innovative ideas from those who think outside the mainstream box.

They are the folks I listen to, not those always banging their chest to reemphasize the importance of their presence here.

Many here try to provide lessons learned for our own stage in the learning process so others don't repeat our mistakes. Don't be bothered by the minority who poke holes in others while they prop themselves up for others to admire.

I appreciate your contributions and interest in sharing the passion we all experience on the water.
__________________

__________________
Al

Custom Google Trawler Forum Search
FlyWright is online now   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





All times are GMT -5. The time now is 01:16 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2006 - 2012