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Author Topic: How to diagnose Exhaust Riser plugging?  (Read 862 times)

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Breakin Away

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How to diagnose Exhaust Riser plugging?
« on: May 27, 2018, 07:41:04 PM »

Hi all,

As some of you may have seen on another thread, I replaced the impeller on my Sherwood pump before splash, and immediately after splash experienced severe (4 drops/second) leakage from the weep holes. I replaced it with a brand new Sherwood G908 from Westerbeke (yes, I know that's a bad idea, but I had reasons that were specific to me). The new pump is generally better, weeping only about 1 drop per minute. However, my expectation was that zero drops should be seen on a brand new pump (unless there's some break-in period that I'm not aware of). I'll call the Westerbeke distributor Tuesday to inquire about whether I have a defective pump.

While there is absolutely no reason to believe that this leakage is caused by backpressure from a blockage or other problem in my heat exchanger or exhaust system, I do need to consider this possibility (especially since I expect that the Wb distributor will try to pin the blame on something else). I see lots of stuff on the Tech Wiki about replacing the exhaust riser, but not much about diagnosing the existing system to see if I actually have a problem there. Do any of you have any tricks to diagnose this without having to dismantle my exhaust riser, etc? Please post here or provide a link to existing posts/articles on the topic. Next time I'm at the boat I'll also remove the HX end plate to inspect, though last time I did this everything looked fine and I've never lost any impeller blades or anything else since then.

« Last Edit: May 27, 2018, 08:20:30 PM by Breakin Away »
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Stu Jackson

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Re: How to diagnose Exhaust Riser plugging?
« Reply #1 on: May 27, 2018, 08:30:42 PM »

>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>The new pump is generally better, weeping only about 1 drop per minute. However, my expectation was that zero drops should be seen on a brand new pump (unless there's some break-in period that I'm not aware of). I'll call the Westerbeke distributor Tuesday to inquire about whether I have a defective pump.
>>>>>>>>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>

I've just completed a rebuild of our rw pump, second time.  Weeping should be ZERO.  Period.  NONE.  Nada, zip, zilch.

The seals are where it could leak.  Indeed, the ONLY place.

I do not understand any possible connection between the riser and the rw pump.  The riser is air, until the nipple.  If you need to know, take the hose off the nipple and look inside.

I think you're over-complicating a simple defect:  your new rw pump is leaking.

Ahh, well, whaddya expect, it's a Sherwood.  :D:D:D

Care to explain "Generally better?"  Really?
« Last Edit: May 27, 2018, 08:31:49 PM by Stu Jackson »
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Breakin Away

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Re: How to diagnose Exhaust Riser plugging?
« Reply #2 on: May 27, 2018, 08:50:56 PM »

....I do not understand any possible connection between the riser and the rw pump.  The riser is air, until the nipple.  If you need to know, take the hose off the nipple and look inside.

I think you're over-complicating a simple defect:  your new rw pump is leaking...
No seal can withstand infinite pressure. So if there's a blockage building up in the HX or in the injection elbow, it could cause leaking through the seal.

Care to explain "Generally better?"  Really?
One drop/minute is generally better than four drops a second. Roughly speaking, it's 360x better.
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Stu Jackson

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Re: How to diagnose Exhaust Riser plugging?
« Reply #3 on: May 28, 2018, 06:49:31 AM »

I hear you.  I do not recall your earlier experience, so perhaps a link to that discussion would be helpful, and we could see for ourselves the "improvement."  :D  I usually can keep track of them, but I've had my own "boat issues" these last few weeks...

You're right, it shouldn't be leaking at all.

If I understand your drift, you're indirectly asking if the vendor could wiggle out of responsibility.  Then it would appear that any backpressure would have to be pretty hefty to blow a seal.  If water is coming out of your exhaust hose through the muffler, and your intake strainer is clear, wouldn't that preclude and claims for pressure related issues?
« Last Edit: May 28, 2018, 06:53:04 AM by Stu Jackson »
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KWKloeber

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Re: How to diagnose Exhaust Riser plugging?
« Reply #4 on: May 28, 2018, 09:41:10 AM »

R,

I had previously emailed you a procedure;

1) Ck for Blockage in the heat exchanger tubes. Pull the caps and make sure the tubes are clear (coat hanger).

2) pull the hose on the injection wye, make sure there is no blockage (feel down into the wye with a coat hanger or something like a short dowel with a larger diameter.

***********

You could also pull the RWP to Hx hose and apply dock water (throttle down the flow/pressure), while you leave the muffler drain open. Only a SMALL amt of water, you don’t want to flood the muffler/riser. Or use air pressure to check for free passage.

In 30 yrs pf pumps, I have not seen a bad Sw pump out of the gate.  By “bad”, I don’t mean “crap“ (it is) I mean “defective.” 

I believe but have no numbers to back it up, that either pump won’t develop enough pressure to blow a seal.

-k
« Last Edit: May 28, 2018, 09:44:29 AM by KWKloeber »
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KWKloeber

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Re: How to diagnose Exhaust Riser plugging?
« Reply #5 on: May 28, 2018, 09:56:01 AM »

Oh also. Did you get a pic of your PO setup?  What size is the inlet elbow/hose?

-k
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Breakin Away

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Re: How to diagnose Exhaust Riser plugging?
« Reply #6 on: May 28, 2018, 10:21:36 AM »

Thanks, Ken. Sorry, I had forgotten that your prior emails had mentioned this.

You were correct all along, my inlet barb is 5/8", per the factory setup. When I changed my impeller 2 months ago (on the hard), I pulled only one hose off to be able to maneuver the pump into position to remove the (stuck) impeller. I thought it was the inlet one, but it was actually the outlet. I had a vivid memory of seeing (and measuring) the 7/8" barb, but it was the outlet barb that I had seen, not the inlet.
...In 30 yrs pf pumps, I have not seen a bad Sw pump out of the gate.  By “bad”, I don’t mean “crap“ (it is) I mean “defective.” 

I believe but have no numbers to back it up, that either pump won’t develop enough pressure to blow a seal.
Yes, this does appear to be an odd case. If the pump doesn't develop enough pressure to blow a seal (which makes sense, since I would expect the impeller fins would just start to bend and leak) and you haven't seen a defective pump before, then one way or another we're looking at a new first.

One other comment, which I'm sure is going to get you saying "I told you so," I was very unimpressed with the condition of the pump housing. It was in a fully unopened box with blue plastic protectors in the threads and over the flange, but the flange end had some significant dings in it. It shocked me enough that I snapped a picture. I don't think these dings would affect performance, but it still gives a very poor impression of quality. In the two pics below, you'll see the new pump with dings, and then my old pump with pristine flange section. [EDIT: These dings actually give the impression that this pump might have been (abused and) returned before, and then re-packed in a fresh box by Westerbeke. Not sure, but something must have caused those dings in the flange.]

Obviously my original intent to have in immediate drop-on replacement is not going to work out. I did get to do some sailing this weekend, but now the boat appears likely to have to go out of service while I work out this issue. It's frustrating, but I've also got a flaky depth sounder that I need to fix, so that would have been taking away from some sailing time anyway.
« Last Edit: May 28, 2018, 11:39:43 AM by Breakin Away »
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KWKloeber

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Re: How to diagnose Exhaust Riser plugging?
« Reply #7 on: May 28, 2018, 11:24:42 AM »

Did it come from a reputable Wb dealer? A Wb distributor? Depco?

That doesn’t look pristine, wonder if it’s a return?

A small drip like that won’t affect performance or your sailing while you have some time off.

-k

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KWKloeber

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Re: How to diagnose Exhaust Riser plugging?
« Reply #8 on: May 28, 2018, 11:32:45 AM »

<<When I changed my impeller 2 months ago (on the hard), I pulled only one hose off>>

Ahhhh. (I’m not beating you up, just making a point to everyone about ‘complete info”.)

 With that info in hand I could have guaranteed you had the OEM sizes.  You can’t repkace the impeller by removing only the inlet hose, so I’d know you defo measured the 7/8” outlet barb.

Even what may seem like an insignificant detail can help sleuth a problem. :D 😳
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Breakin Away

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Re: How to diagnose Exhaust Riser plugging?
« Reply #9 on: May 28, 2018, 11:44:28 AM »

<<When I changed my impeller 2 months ago (on the hard), I pulled only one hose off>>

Ahhhh. (I’m not beating you up, just making a point to everyone about ‘complete info”.)

 With that info in hand I could have guaranteed you had the OEM sizes.  You can’t repkace the impeller by removing only the inlet hose, so I’d know you defo measured the 7/8” outlet barb.

Even what may seem like an insignificant detail can help sleuth a problem. :D 😳
All that's correct, and you were right all the time. I didn't know what "complete info" I needed until after I left the boat (in Maryland) and flew to Milwaukee for the week. It's the cost of having a long-distance job. Even when I'm at home, I'm still 2 hours away from the boat, so long-distance diagnoses are really difficult. And every time I'm driving home from the boat I get a flood of ideas on what else I should have done to diagnose xyz problem.
« Last Edit: May 28, 2018, 11:58:37 AM by Breakin Away »
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Breakin Away

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Re: How to diagnose Exhaust Riser plugging?
« Reply #10 on: May 28, 2018, 11:53:05 AM »

Did it come from a reputable Wb dealer? A Wb distributor? Depco?

That doesn’t look pristine, wonder if it’s a return?...
Hard to believe that it came out of the factory that way, but the box showed no signs of having ever been open.

I bought it from Hansen Marine, who is the authorized distributor for eastern Pennsylvania, where I live. I'll be on the phone with him tomorrow. If I've lost the opportunity for a quick turnaround swap-out, I'd actually prefer to rebuild my old pump. I'm going to search the Tech sections right now for Ron Hill's Sherwood rebuild instructions. I'll try to take apart the old pump today if I have the right tools here. Maybe I can get the needed parts in quick enough to ask Hansen to take the pump back and keep it (if the shaft is in OK shape).
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KWKloeber

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Re: How to diagnose Exhaust Riser plugging?
« Reply #11 on: May 28, 2018, 12:44:11 PM »

Hansen is reputable. It’s hard to believe it came from Sherwood that way.

  If Wb manufactured it, then i wouldn’t doubt it. I’ve posted before that I had to return nearly $1000 in parts, multiple units that were mis manufactured and Wb didn’t catch it and shipped them out. Double threaded risers, ports with threads not cut to full depth, exh flanges with threads on only half the ID circumference.  All offshore no doubt.

What I’ve seen that is manufactured in house is ok.

Ken

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Breakin Away

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Re: How to diagnose Exhaust Riser plugging?
« Reply #12 on: May 28, 2018, 12:55:53 PM »

FWIW, I'm starting to take my old pump apart. Both the gasket and O-ring are perfectly seated, eliminating the possibility that they were the source of the leak. Looks like it definitely came out of the weep hole. (Couldn't trace the rust stain, because the leak was so fast that water rusted the entire iron body.) Impeller looks great also, since that was replaced just before all this weeping stuff started.

Interestingly, my copper C-clip is not rusted at all. In fact, it's in really good shape. Of course, Murphy's law guaranteed that my snap-ring tool (which I've only used once) is at the boat (2 hours away). So it's off to the store to buy another one (that I will probably only use once).

If there is scoring on the shaft, where would I see it? Ron's tech article sounds like I may only need a couple of water-side bearings and a stainless steel C-clip replacement. So I don't need a total rebuild kit (especially with the new impeller already in there)? Are there other recommended parts?
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KWKloeber

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Re: How to diagnose Exhaust Riser plugging?
« Reply #13 on: May 28, 2018, 01:06:07 PM »

I’m not familiar with rebuilding a Sw, ‘er Wb pump, but I’d imagine scoring would be at the seal, where it tends to show up in in Ob. A worn bearing or shaft at that location would tend to wear/elongate the seal.

Since you’re “down” why not just replace w/ the Ob and “be done with it”?

-k
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Ron Hill

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Re: How to diagnose Exhaust Riser plugging?
« Reply #14 on: May 28, 2018, 02:27:39 PM »

Breaking : To check if there is a blockage in the exhaust water system (from the raw water pump to the HX to the riser to the muffler) 
Just take off the hose from the RW pump and blow into it.  It should be free!!


A thought
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