420/44 DB Owners Club

Alex,

I change my impellers annually (in the spring) that's why I don't worry about pulling them in the fall. I would think the only reason to do it more often is if you were concerned they got damaged somehow, sucked sand, seacock closed, etc.

I also change my genny oil mid season, this year I did it at 154 Hours. I should have waited a little bit longer because end of year time on oil was 205.9.

It doesn't bother me too much because of the oil report from Blackstone:
All wear read below averages for this type of engine, which is a very good indication of normal wearing parts and is especially good considering this oil was run longer than average. Universal averages show normal wear after about 120 hours use on the oil. Insolubles (oil oxidation and soot due to heat, use and blow-by) were low at a trace, showing good oil filtration. No fuel or anti-freeze was found. Low silicon shows good air filtration.

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I've always changed impellers in my big boats every 2 yrs. In 20+ years I've only had to chase vanes down once that I can remember and I've never pulled them when winterizing. If total piece of mind is what you're after, replace them annually or pull them when you winterize. I did change one mid-summer this year when I had a dumba$$ attack and forgot to open a seacock back up after cleaning the strainers.

I try to change gen oil between 100-150 hours and at the end of the year. We put just over 400 hrs on the westerbeke this summer. Gen oil sample was pretty clean, no abnormal wear or high trace, on 112 hr sample.
 
I would suggest watch the impeller closely at 180 hours. Changing oil at 200 hours is always a good idea. Delo oil has never let me down in the application. My oil sample over the years would indicate good results.
 
Thanks for your suggestion, guys. It looks like I have new game plan for the next season regarding generator oil and impeller change.

I always changed my impellers every other season and was planning to do the same on the mains. In my previous gas boats this was working very well as the impellers looked as new after two season of usage and about 200-250hrs combined between two seasons (I also never pulled the impllers for winter storage). Do you see why the same approach wouldn't work for my diesel engines?
 
Personally, I think changing the impeller every year is excessive... I read some guys on Boatdiesel.com were at 1700 hrs. on the same impeller and still going. Now I'm not saying to do that but it shows you how long they can last. I changed mine this past April since they were original from when I bought the boat. They did come out deformed but kept them and they went back to their original shape. For me, I keep spares on board and the required tools to change them. If there is no water flow, the exhaust has a sendor to set off the alarm. Every other year is fine IMO....
 
This from post #335 above:

2. ..................... sooner or later you will get a wake up call on leaving impellers in a pump housing over an extended period. Here is the text of Sherwood's recommended lay up procedure:

Sherwood recommends replacing your impeller annually.Proper storageof the impellersduring a prolonged lay-up can help maintain the life of the impeller.
Remove the impeller from the housing and store it in a cool, dark place.This will avoid the following:

•Copper bonding of the impeller to the housing
•Vanes “setting”into position as stored in the housing
•Ultraviolet deterioration

Three tips to help you install your new Sherwood impeller:

•Use a non-petroleum based lubricant (silicon or soapy water) to help slide the impeller into the housing.
•Install the impeller with a twisting motion onto the shaft.Never force an impeller onto the shaft.
•Impeller must be able to move freely on the shaft to properly prime and function.

(Use a small amount of non-petroleum based lubricant to help hold the o-ring when replacing the cover.)
*See Maintenance Schedule
Genuine Sherwood TechTips

You will find this on Sherwood's webite under references; 17000 & 26000 Tech Guide (17000 series covers Cat 3116/3126 and Cummins 6BTA; 26000 covers QSC's.)

I had this happen last summer........My wife and I got summer colds from hell on the way to the boat one trip down. We stayed inside for 3-4 days, then got caught up in a tropical storm. We didn't get to use the boat at all that trip. Then a month later, we went back and found no water flow from either engine. The impellers had only one blade left on each one and the remains were in the heat exchangers and stuck to the water pump housing. This was after 6 weeks of inactivity........not a full winter lay-up. Take 'em out; leave 'em in? Doesn't matter to me. Just be prepared to stop the launching process while you replace impellers and fish the old vanes out of you coolers some year when, you least expect or want to fool with it.





I usually run my main engine impellers 200 hours and the generator 300 hours, but we use our boat 12 months a year and run it regularly. I never gave the Sherwood guide a thought and never considered copper bonding of the impeller to the pump housing, but it can happen and the result is ugly:

impeller.jpg


The vanes were "welded" to the pump housing and were ripped away when we started the engine..........and this happened on both sides at the same time to engines that were idle for 6 weeks, but were otherwise well maintained and the impellers had 138 hours on them.

My point here is that if you leave your impellers in over an extended layup, this could happen to you when you least expect it. Be aware of the possibility and carry extra impellers, o-rings, impeller puller, lubricant and what ever hand tools you require to change the impeller in case it happens to you when you leave the impellers in over the winter. So,.......remove the impellers for storage or replace them when you have a problem in the spring, either way requires an impeller change @ 1 hour + $80/ engine for parts if you can get to them. Just be prepared if it happens.
 
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Frank,

Let me get this streight. Your usual interval was 200hrs on mains, in this incident your impeller had only 138hrs. It was sitting for only 6 weeks. This brigs up few questions:

1. How old were the impellers before they failed at 138hrs?
2. What you think was the primary cause of the failure? Is this your main clue "...copper bonding of the impeller to the pump housing..."? Could it be a possibly bad/defective set of impellers?
3. What are you planning to do different? Change them every 100hrs, take them out if you leave the boat for over 30 days?

I'd say that this was an unusual failure, which non of us would expect on exceptionally maintained and frequently used boat.
 
I am tracking a new impeller right now. I just checked it at 200 hours. It is starting to show signs of some memory but no cracks. I had my last one fail at 189 hours. The one I am tracking now is a standard Sherwood. When I am done with this one and figure out how long it last, I will test the long running blue impeller ( forgot the name but have the part number if anyone needs it ). The blue impeller is suppose to be a more durable type and we will see. I spent time with the generator folks at the boat show. They were clear about where you run, how often you lay up the system, temp, sandy water, and what type water, makes a big difference. Knowing all these conditions will help guide how often you check the impeller.
 
Alex F said:
Frank,

Let me get this streight. Your usual interval was 200hrs on mains, in this incident your impeller had only 138hrs. It was sitting for only 6 weeks. This brigs up few questions:

1. How old were the impellers before they failed at 138hrs?
2. What you think was the primary cause of the failure? Is this your main clue "...copper bonding of the impeller to the pump housing..."? Could it be a possibly bad/defective set of impellers?
3. What are you planning to do different? Change them every 100hrs, take them out if you leave the boat for over 30 days?

I'd say that this was an unusual failure, which non of us would expect on exceptionally maintained and frequently used boat.
Click to expand...


Alex,

1. The impellers were about 14 months old when they failed.

2. You know, I really am not sure. I have owned this boat for 16 years, so I've had more than one try at the impeller thing and I've never experienced a failure like this. When I've had others fail, the vane has broken completely off near the hub where the tightest bend on the vane is and every broken vane has looked the same. The looked almost like someone had cut them off with scissors, the tear was so straight. As the photo shows, these looked almost chewed off like the vane was held stationary when the shaft began to turn. The biggest difference was all the rubber stuck inside the pump body. I had to sand the interior of the housing to get it all out.

I know these weren't old impellers and unless Sherwood sold me 2 bad ones at the same time, I don't think they were defective. I change impellers as a regular maintenance item before I ever see signs of a failure because I hate tearing down the heat exchangers to dig out the broken pieces. I do keep spares on the boat, but I don't recycle them because that would mean I would always using impellers that had been sitting in the spares box at least 18 months when I installed them. Instead, I always order new Sherwood parts a few weeks before I plan to change impellers. This time I had to buy them from the marina since I needed them that day.

3. I don't plan to do anything different.......other than not get a summer cold! I've done the same thing with water pumps since I've owned this boat........impellers every 200 hours which is about avery 18 months for me, then new water pumps every 3rd impeller change. We do run the boat all year...in a typical January we may use the boat 7-8 days in a 2 week span. I've never had this problem before and only brought it up when I realized that a lot of you guys up north deal with idle boats for months at a time and never remove impellers. If some of you guys can benefit from my experience or bad luck, then great. At least you now know the copper bonding potential exists.
 
I had a similar failure with impellers in the Sherwood pumps on my Cummins C motors after two seasons. Circumstances were a little different because our season in Michigan is five to six months and at least half the time we are in heated storage so the impellers take a "set" if you leave them in. But we are also in the freshwater of the Great Lakes.
I changed out the Sherwood impellers in the 08-09 winter after two seasons. They were almost perfect with slight cracking of the base of the vanes only. So with the new set I waited two seasons and went to change them again but this time one third of the vanes were damaged and missing. Again only two seasons of 50-75 hrs. per season. It forced me to buy a borescope to pick impeller blades out of the aftercooler. What happened? Why the difference? Were the cages causing the blade tearing?
So I took the opportunity to change the Sherwoods to a couple of SeaMax pumps from Seaboard marine and was immediately impressed by the construction and noticed that they moved more water through the system. No more keyed slot to lose a key down the intake (a frustrating six hour exercise on the port motor) because they were splined. I popped out one impeller this fall after the first season but it was like new and certainly more flexible than the Cummins brand impeller on the previous pumps. I feel more confident in getting two years out of these impellers than the previous set-up.

James
 
View attachment 22260View attachment 22261

This is an impeller that I removed in April after sitting all winter (approximately 4 months). It did have more of a "setting" appearance when I first removed it, but it is completely in tact. I can't confirm the amount of hours on it because it was the original impeller from when I purchased the boat. I know I put about 160 hrs on it myself prior to changing it.

Frank, the failure you show seems highly unusual and the question which has been posed is why? My question would be are the pumps above sea level where they naturally drain and eventually become dry after a prolong period of non use?. I'm certain mine are below sea level therefore always primed. Just a thought.....
 
I pulled mine out of the stbd side (the easiest to get to) just to see what it looks like after 130hrs.

my_impeller_112011.jpg
my_impeller_112011_2.jpg

Based on what I see there should be no reason for these not to serve one more season. If it wasn't for the port side it wouldn't be a much of a question (it took me 1.5-2hrs to change that one last spring).
 
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Ahhhhh, the port side..... I am doing mine in the next two weeks. Some brilliant guy sure made our lives hell back during the design process.
 
You would think they would be able to mount the water pumps on either side of the engine for ease of access?

That would make too much sense though.

Doug
 
I've heard from a friend with 400DB that he had mechanic walking away from doing this job on his 3126CATs. Now that sucks big time....
 
The water pumps are gear driven by the engine's accessory drive mounted on the rear of the timing cover. That would certainly make mounting on both sides of the engine difficult.
 
Frank,

I agree that sometimes it takes way too much of rearranging of major components to achieve small results like access to a sea water pump that you touch once a year at most. By now, most professional mechanics can do the job in decent time frame as they have all necessary tools and the knowledge to tricks.

I think it's a good time to ask for some tips on what might be a better way to change the port side pump? Last spring I did it for the first time. I didn't like the idea to lay on the engines and have my head with both arms hang down, but I know that this is the only way for some people to do it. Since I'm not a big guy I used it to my advantage and I'm able to position myself between the front end of the engine and the bulkhead. It's tight, but I fit in the space my boat has. I know in 400DB it's a tighter space. So, by puting some kind of coushin I can lay on the right side and reach the pump with only right hand. With my left hand I hold the telescopical mirror, but most of the work is done by feel.

Anyway, the primary two methods I know are:

1) Change the impeller with the pump in place. This is much harder since most of the work is done in akward position with one hand.
2) Take off the whole sea water pump (I think it's held by only two bolts). This should be much easier as most of the work can be done with pump on a bench.

I've used method #2 only on my gas boats with belt driven pumps. But, due to the fact that I'm still learning everything about diesel boats I felt that it'll be much safer approach to use method #1. At least I'm just messing with the impeller with key, gasket and a cover with 3 bolts. Not too much that can be messed up, as long us I can remain in that position for a while. As I mentioned earlier, it took me somewhere around 1.5hrs or so. I thought that it's still not too bad since the stbd side is really a pleasure to do. Coming from 320DA, where both pumps are a PITA that takes at least 1-1.5hr each, I thought this isn't that bad or at least not worst than what I had before.

The question is, what is the trick, what's involved and how difficult to take the whole pump off so I can do the impeller swap in my hands away from the engine? What are things to watch out for that can go wrong, parts to loose, etc....?
 
There will always be one side that is a bear to deal with and it's the starboard side on my V-drives. Drop the pump if possible and you will save hours of work. Four bolts on the outlet elbow, then two on the pump body and let the pump swing on the inlet hose. At that point you can get at the last four bolts of the intake elbow. You can leave the pump in place on the "easy" side to change your impeller. Good luck.
 
Any suggestions as to good ways to plug up the bilge vents in the sides of the hull? I am trying to make sure my warm air from the bilge heaters stays in the bilge rather than venting out.

Last year I used some masking tape, but there has to be a better way. Preferably something that's easy to remove/reinstall for those nice winter day boat rides...
 
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