Registered users don't see ads

How long mixing elbows last/reduced flow

Discussion in 'Ask All Sailors' started by Skipper, Nov 11, 2017. Add this thread to a FAQ

  1. Skipper

    Skipper

    Joined Oct 9, 2008
    1,365 posts, 147 likes
    Bristol 29.9
    US Dana Point
    -update 11/13 below-
    How long do mixing elbows last?
    Mine in 6 years old. About 300 hours. Looks new (pic).
    ....on the outside.
    I suddenly have reduced raw water flow. Pacific salt water last 2 years. Upper Chesapeake previous 4.
    I checked the through hull inlet, gusher. Checked sea strainer outlet, much less water. Yet no restrictions. I put the strainer in 2 years ago. Boat didn't have one previous 32 years.
    So I bypassed the strainer. Same low flow at the exhaust. Maybe a quarter of what it should be.
    Very recent impeller. Oberdorfer pump. But put another new impeller in just to check. Same problem.
    I had checked the HX a couple months ago, looked clear. But it's the original (1984) Universal 2" with only 1 end cap. Can't see the zinc pencil end, but poked around in there with a wire and it seemed clear.
    I'm wondering is it the HX clogged where I can't see it, or the mixing elbow. Or...
    Any comments appreciated.
     

    Attached Files:



    Last edited: Nov 13, 2017 at 12:01 PM
  2. Bill Roosa

    Bill Roosa

    Joined Jun 6, 2006
    6,871 posts, 103 likes
    Hunter 40.5
    US Harrington Harbor North, MD
    They last as long as exhaust manifolds. They do require the occasional cleaning though if you operate the engine at low power levels a lot.
    Your gusher at the inlet thru-hull and no gusher at the strainer is probably because the strainer is higher up nearer the water line. a strainer above the water line will not even have water flow!!!
    think you diagnosed the problem by tracing along the flow path. has to be the HX or elbow.
     


  3. Stu Jackson

    Stu Jackson

    Joined Feb 26, 2004
    19,490 posts, 361 likes
    Catalina 34
    US Maple Bay, BC, Canada
    How can there be less water there if you say "no restrictions"?

    Unless Bill is right in his assumption. My strainer is below the waterline.
     


    Last edited: Nov 11, 2017
  4. jibes138

    jibes138

    Joined Jan 27, 2008
    2,713 posts, 79 likes
    ODay 35
    US Beaufort, NC
    What kind of mixing elbow do you have? Is there a 90 degree fitting? Those can clog with salt. Do you have flow at the hose going into the HX? Do you have flow at the hose going into the mixing elbow?
     


  5. Whatfiero1

    Whatfiero1

    Joined Mar 29, 2017
    116 posts, 13 likes
    Hunter 30t
    US littlecreek littlecreek
    yes check that 90 deg fitting right where raw water goes into exhaust elbow the cold salt water hits hot exhaust steel and evaporates and causes a salt blockage if ya can trade out that fitting for a straight
     


  6. NYSail

    NYSail

    Joined Jan 6, 2006
    1,541 posts, 37 likes
    Beneteau 423
    US Mt. Sinai, NY
    Pull the water inlet hose off the elbow and see flow...... then if nothing odd just remove the elbow itself
    And inspect. My yanmar elbow was good for 9 seasons before it clogged. Some people just clean them...... I am of the replace school if they are bad.
     


  7. Skipper

    Skipper

    Joined Oct 9, 2008
    1,365 posts, 147 likes
    Bristol 29.9
    US Dana Point
    Thanks all.
    Great idea to check the flow at the HX outlet/elbow inlet. I sort of thought of that but didn't want to climb in the rear -engine access, have salt water in the engine bay to rinse and clean, etc. Lazy! After I'd been wrenching an hour, just wanted answers. The answer is continue checking the flow further downstream.

    So I've never cleaned an elbow.
    If this turns out to be the problem...
    Do you just remove it and reach in the ports with tools? Can you get all the up to the angle? Any hints.
     

    Attached Files:



  8. StargazerP303

    StargazerP303

    Joined Oct 22, 2014
    146 posts, 17 likes
    Pearson P303 #221
    US RockPort Maine
    My engine is a 2GMF and installed a new elbow 4 years ago. Upon inspection each year I've noticed a buildup each year more year 2 and a lot year 3. It seems to build up faster when the old buildup isn't removed and put back into service. It does seem though the exhaust oil/fuel collects more when its cool. So I myself will remove and clean every 3-4 years baring any issues. I put mine into the oven and did a clean-cycle. when done it looked new.. But that's me! However, Make sure you soak in hot water for a day before putting into oven. It prevents a possible fire. lol
    Regards Capt. Rob
     


  9. Calif. Ted

    Calif. Ted

    Joined Jun 8, 2004
    1,964 posts, 60 likes
    Catalina 320
    US Dana Point
    On my Perkins the elbow was just a 45 degree bend and would last 600 hrs. before the exhaust passage would clog. I cleaned it once using a grinder with a round rotary rasp on it, took 2 days and made an incredible mess. The "coke" that forms is hard as a rock. A couple days later while at a radiator shop leaning on a bead blasting cabinet a better possible method dawned on me :banghead:. The 3 piece 180 degree elbow on the Yanmar I replaced right after I got the boat at 300 some hrs. and recently again at 650 when it clogged, partly my fault, I don't run it much or hard enough. Part of the problem with cleaning them is the water passage runs up around the bend and it's mostly inaccessible.
     


  10. Allan12210

    Allan12210

    Joined Jan 22, 2008
    1,333 posts, 90 likes
    Hunter 34
    US Alameda CA
    I have to clean mine every season just so it won't clog up. See photo.
    20160211_154450.jpg
     


  11. Rick D

    Rick D

    Joined Jun 14, 2008
    6,340 posts, 116 likes
    Hunter Legend 40.5
    US Long Beach, Shoreline Marina, CA
    When I had a 3GM, I had elbow problems at the injector. I purchased a stainless steel spring, about 6" long and put it in the bit of my drill and, while squirting carb cleaner, ran it in and out few times. Kept it clean. Did it once a year.
     


  12. Allan12210

    Allan12210

    Joined Jan 22, 2008
    1,333 posts, 90 likes
    Hunter 34
    US Alameda CA
    I'm intrigued by this. Is it a long, small diameter spring? So you can Roto-Rooter the entire water passage part of the elbow through the little (3/8" NPT) hole?
     


  13. Whatfiero1

    Whatfiero1

    Joined Mar 29, 2017
    116 posts, 13 likes
    Hunter 30t
    US littlecreek littlecreek
    I blame the 90 deg. Slows the water down or something straight fitting seems to fix
     


  14. Rick D

    Rick D

    Joined Jun 14, 2008
    6,340 posts, 116 likes
    Hunter Legend 40.5
    US Long Beach, Shoreline Marina, CA
    It worked for me. The passage that was carbonized was at the elbow's junction with the pipe nipple. And the spring moving around seemed to clear (with the carb cleaner) the immediate area. Yes, small OD spring in a drill chuck. Actually, it may not have been SS; probably wasn't.
     


  15. Skipper

    Skipper

    Joined Oct 9, 2008
    1,365 posts, 147 likes
    Bristol 29.9
    US Dana Point
    YIKES!
    Good idea to check the raw water flow at the elbow inlet.
    Disconnected the hose, put bucket under it, turned motor on.
    Trickle. Like a dog peeing. Maybe a quart a minute.
    So it's the HX.
    I decide to check the pump output just in case. Remove the HX raw inlet hose at the bottom of the HX, and see this:
    image.jpeg

    The odd thing is that the rods are clear inside.
     


  16. Skipper

    Skipper

    Joined Oct 9, 2008
    1,365 posts, 147 likes
    Bristol 29.9
    US Dana Point
    Turned out only that HX inlet elbow was clogged. Minor calcification elsewhere. Cleared it out. Also replaced the hose from pump to HX; it was too small a diameter and a hodgepodge of 2 lengths of hose (pic). Probably from when the yard monkeys installed the new Oberdorfer pump 6 years ago. - I should have done it myself.

    I think the raw water filter I installed 2 years ago restricted the flow, causing calcification to build up.
    It never caught anything other than little plant bits, and the motor ran without it for 32 years previous. So I removed it.

    Rapid flow now. Didn't have to replace HX nor mixing elbow.
    Total repair cost: $8. (Hose)

    image.jpeg
     


    Last edited: Nov 13, 2017 at 12:14 PM
    Allan12210 likes this.
  17. Warren Milberg

    Warren Milberg

    Joined Dec 1, 1999
    2,308 posts, 67 likes
    Hunter 28.5
    US Chesapeake Bay
    The OEM mixing elbow on my 1986 Yanmar 2GM20f lasted about 25 years...and it was nice enough to give plenty of early warning (reduced max rpms) that it required attention.
     


  18. Allan12210

    Allan12210

    Joined Jan 22, 2008
    1,333 posts, 90 likes
    Hunter 34
    US Alameda CA
    Yes, mine lasted 25 years as well. But it wasn't as kind to me when it broke in half. Other than the annual cleaning of the water inlet fitting, I only cleaned the rest of it a couple of times during that period. I am going to change that little fitting to a straight one and am looking forward to trying the spring that Rick D has posted about for annual cleaning. The close nipple with both left and right hand threading is a real weak point. It's made of stainless and can only be inspected easily by complete disassembly. I have located a reference to a black iron or galvanized right hand/left hand 1-1/2" NPT threaded hexagonal nipple here:

    http://www.gfps.com/appgate/ecat/common_flow/100071/FIT/en/497226/497233/P121799/product.html

    I haven't followed up on it as a potential spare that might last longer as its the same material as the two cast pieces of the exhaust elbow.
    Broken.JPG
     



Turn any toilet into a Raritan for a fraction of the cost
The Raritan LBA matches your existing bowl with the pump/plumbing of a PHII or PHC. save!
Gray Enterprises port gasket
Stop winter leaks. Compare our price!
Mainsail covers
Pre-patterned mainsail covers to fit your boat
Noflex Sewage Treatment
Treat sludge and odor problems in holding tanks.