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Author Topic: Poor exhaust water flow  (Read 421 times)

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Ross Fisher

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Poor exhaust water flow
« on: January 15, 2019, 11:26:30 PM »

Checked my Heat Exchanger today by removing both end caps and examining end chambers and tubes for blockage or contamination. Seemed all OK after removing lumps and scraps of old Zincs and some seagrass. Replaced Zinc, started and test ran the engine and observed very poor flow of cooling water from the exhaust. Temperature did not go above 160, but this concerns me. What steps should I follow to investigate this problem? Thanks for your knowledge.
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Ross Fisher
# 1486  "Avventura"                            
2000 Catalina Mk11 Wing Keel
M35B
Melbourne, Australia

KWKloeber

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Re: Poor exhaust water flow
« Reply #1 on: January 16, 2019, 03:03:13 AM »

[EDIT]
https://marinehowto.com/external-strainers-omg/
https://marinehowto.com/westerbeke-universal-marine-heat-exchanger-cleaning/


Ross,

The first question is poor flow, based on .... ?  What's your gauge for good vs poor? Did you see a recent change?  Since....when ?

IIWMB, I would troubleshoot where the flow changes from good to poor (or vice-versa,) i.e., systematically/sequentially remove the seawater hose at different spots along the "chain" (most convenient locations first) and determine if flow is poor at the SUPPLY TO the seawater pump, right AFTER the pump (due to the pump itself,) or there's a restriction after the pump (Hx tubes, the injection wye above the muffler is sometimes a place for deposits, exhaust hose, etc., etc....)

Might you have a clogged thru-hull, seacock, strainer, etc. - first place I would check unless you know those are ok.   Does she have an external strainer?

You can "rod" each Hx tube by running a stiff wire ("coat" ie. (shirt) hanger or rebar tie-wire) thru each Hx tube to make sure that all are clear. 

What's the age -- might the Hx need to be removed and cleaned of scale (by a radiator shop or using RydLyme)?  If so, pressure-test it at the same time if age is suspect -- you don't want to put 'er back together and have a pinhole leak between the sea water and coolant sides (which also occurs with age.)

-ken
« Last Edit: January 16, 2019, 03:09:04 AM by KWKloeber »
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
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Explore.  Dream.  Discover.   -Mark Twain

Ken Juul

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Re: Poor exhaust water flow
« Reply #2 on: January 16, 2019, 06:00:18 AM »

every time I have had reduced flow it has been from barnacles growing in the intake.  Have a diver check from the outside or remove the strainer and use a length of wooden dowel to remove any resrictions.  Once you find the right size dowel, put a string around it and hang it from the fuel pump for next time.
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scgunner

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Re: Poor exhaust water flow
« Reply #3 on: January 16, 2019, 08:28:13 AM »

    Ross,

       If you're running 160 on your temp gauge whatever's going on with the cooling system it's still providing enough water to cool the motor. If you're not getting enough flow as you suspect you should also be getting some steam. When I've had low flow and steam it usually means a vane has broken off the impeller and gotten stuck in the system. One quick non-scientific way to check the flow, stick your hand under the stern where the water exits the boat. If the flow is adequate the water should be warm not hot to the touch.
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Ed Shankle

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Re: Poor exhaust water flow
« Reply #4 on: January 16, 2019, 09:03:31 AM »

Ross, also remove the raw water hose at the HX end and check the inside of the HX nipple for a blockage. Iíve had it happen a couple of times. It builds from the edges inward, slowly enclosing the center. Stu has noted it previously too and thinks it is salt. I thought it may be calcium, but never tested it. You can break it up easily with a screwdriver.
Good luck,
Ed
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Ed Shankle
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Ross Fisher

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Re: Poor exhaust water flow
« Reply #5 on: January 16, 2019, 03:36:00 PM »

Thanks all for the suggestions. I will undertake a systematic examination of the raw water plumbing, as it seems highly likely that there is a blockage or severe restriction somewhere in there.
Ken, to respond to your question, the flow of exhaust water has dropped from the expulsion of about a pint every 3 or 4 seconds at fast idle, to expelling a pint every 15 or 20 seconds. This, coupled with a bit of steaming at cruising speed causes my concern.
Ross
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Ross Fisher
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Mick Laver

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Re: Poor exhaust water flow
« Reply #6 on: January 16, 2019, 06:21:54 PM »

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Ron Hill

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Re: Poor exhaust water flow
« Reply #7 on: January 20, 2019, 01:16:21 PM »

Ross : Have you checked your impeller to make sure all the blades are there??
Every spring I checked mine and reversed it when I reinstalled.

A thought
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Ross Fisher

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Re: Poor exhaust water flow
« Reply #8 on: January 22, 2019, 02:24:34 AM »

Ron, I checked the impeller today and it was fine, although I suspect that the gasket was faulty and I had an air leak. Replaced the gasket, did not think to reverse the impeller, tested it and all was back to normal. This was after going through the entire raw water plumbing system, rodding the Heat Exchanger, checking all connections and cleaning all narrow flow points. All members advice pointed me to a logical approach. Many thanks to all contributors.
Ross
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Ross Fisher
# 1486  "Avventura"                            
2000 Catalina Mk11 Wing Keel
M35B
Melbourne, Australia

KWKloeber

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Re: Poor exhaust water flow
« Reply #9 on: January 22, 2019, 08:05:36 AM »

Ross

Good deal.  Glad you located (hope) the root cause. 

I presume you have the OEM Sherwood pump; not an Oberdorfer.  On the older OBs, there was sometimes the issue of the impeller not sealing well (faulty impellers-not sealing against the cover, the cover worn inside and/or too heavy a gasket which caused a low flow situation.  One thing that helped seal the gasket was to apply a very light film of superLube to the two faces (cover & body) before assembling the pump.

-ken
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain

Freedom

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Re: Poor exhaust water flow
« Reply #10 on: February 02, 2019, 09:45:38 AM »

Ross,

Had a similar issue this year during a trip to Catalina Island from San Diego. Engine was running hot but not overheating so I decided to just lower my RPMs and nurse her to Catalina where I could trouble shoot the problem. I started by diving under the boat and checking the through hull, I then checked the sea strainer and impellor. I found that all was OK so I figured it must be the heat exchanger. I removed the end caps and all seemed ok so I put it all back together but the engine still ran hot. I decided to go for it and remove the heat exchanger to get a better look, and also check all the hose for blockage. Its a good this I removed it because it turned out that a majority of the small tubes where totally blocked with calcification. I was able to find an old antenna whip at the local repair barge and used it as a ramrod to clean out every tube. I also soaked the unit in some muriatic acid that I got from the hardware store, that really cleaned out every last bit of corrosion. I reassembled, fired up the motor and was good to go with engine temps back at normal range. Let me say that our trip home was a lot less stressful that the trip there.
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