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Raw Water Fitting Came Loose from Heat Exchanger

Discussion in 'Engines and Propulsion' started by dkerphunter, Mar 22, 2018. Add this thread to a FAQ

  1. dkerphunter

    dkerphunter

    Joined Jul 6, 2013
    34 posts, 2 likes
    Hunter 336
    CH Société Nautique de Genève
    Hi. I recently found water in my Yanmar 3GM30F engine compartment. The raw water outlet hose connector of the heat exchanger worked loose. I have no idea how. The set screw was tight. I thought it could be caused by pressure buildup but the raw water is discharging nicely, so there's no blockage. I took off the side cover, loosened the set screw, pushed the connector back in fully, tightened the set screw and reattached the side cover. I didn't have a replacement gasket for the heat exchanger side cover.
    • Where can I source a replacement gasket (RESOLVED: Toad Marine)?
    • Any ideas what would cause the outlet hose connector to work loose?
    Thanks.

    Heat Exchanger.png
     

    Attached Files:



    Last edited: Mar 30, 2018
  2. kloudie1

    kloudie1

    Joined Nov 6, 2006
    7,612 posts, 421 likes
    Hunter 34
    US Mandeville Louisiana
    I have never seen one with a 90 degree fitting on the inlet.. Check the gasket (packing) and look carefully at the sealing faces on the cover and the cast iron heat exchanger body.. any corrosion or debris there can cause a leak..
    Any Yanmar dealer should be able to get the gaskets for you. Some parts of the European Yanmar are different so that may be why they aren't common here in the USA.
    Post a picture if you can.
     


  3. JamesG161

    JamesG161

    Joined Feb 14, 2014
    2,390 posts, 568 likes
    Hunter 430
    US Waveland, MS
    Running with a partially restricted discharge , like your muffler?
    Jim...
     


  4. Tally Ho

    Tally Ho

    Joined Jan 7, 2011
    920 posts, 109 likes
    Oday 322
    US East Chicago, IN
    Does that 90 degree fitting screw into the side cover or is there a nut on the inside?

    I don’t understand how it could “unscrew” with a hose holding it in place.

    Greg
     


  5. dkerphunter

    dkerphunter

    Joined Jul 6, 2013
    34 posts, 2 likes
    Hunter 336
    CH Société Nautique de Genève
    Greg, The elbow fitting doesn't screw in. It is fastened in place by a set screw. See the attached drawing. It's a mystery how it came lose. There is a barb on the shaft of the elbow fitting that fits into the end cover, presumably to be caught under the set screw. I think maybe the barb wore down allowing the shaft to slip out in spite of the set screw, which was completely tightened down. I've ordered a new elbow fitting and set screw to be on the safe side. Dan
     

    Attached Files:



  6. JimInPB

    JimInPB

    Joined Aug 22, 2017
    579 posts, 161 likes
    Hunter 212 & 170
    us West Palm Beach
    That heat exchanger is what is known in my circles as a tube & bundle type heat exchanger. Most of my experience with them comes from their use on industrial chemical processing equipment. That diagram shows 3 passes through the tubes & a single pass in the shell. That routing is optimized for maximum temperature change on the tube side & minimum temperature change on the shell side. It does not make sense to me why you would want that.

    I can understand why you would want the sea water in the tubes rather than the shell. You want to be able to flush the seawater when the boat is hauled out & you don’t want crud collecting in the shell. Tubes are easy to clean once the heads are off. But, if the seawater is going to be in the tubes, I would think that you would want all tubes flowing in parallel to minimize the average temperature in the tube side liquid & maximize heat transfer from the shell side liquid. If the seawater were in the shell side, then the 3 pass routing in the tubes would give an optimized delta T. In the configuration shown, I would only expect the heads to be gasketed & configured for a 2 pass routing if you needed to send the tube side liquid in & out from the same end. Does anyone know why you would want to break up the tubes into 3 groups of 8 for 3 passes? It seems counter-productive to me.

    Also, in my experience, it improves the lifespan of the heat exchanger to put the shell side inlet on the opposite end from the tube side inlet.

    As for the fitting that came loose, does it have an O-ring on it? What makes the actual seal if there is no O-ring? What type of set screw was used? Set screws come with different types of points for different uses. A dog point would only be recommended if it were going into a full diameter pilot hole or groove. A cone point would be used if it were going into a small diameter pilot hole. Cup points bite into the surface below them well. Knurled cup points are also self locking to a certain extent & resist coming loose. http://www.atlanticfasteners.com/tech-tips/set-screw-point-styles-and-their-use/
     


    Last edited: Mar 30, 2018
  7. dkerphunter

    dkerphunter

    Joined Jul 6, 2013
    34 posts, 2 likes
    Hunter 336
    CH Société Nautique de Genève
    Impressive heat exchanger knowledge! I can't comment on the heat exchanger design. It's the standard one Yanmar provides on these marine engines. Your guess about the raw water being in the tubes sounds right. The tubes do run parallel, except near the ends where they bend to channel water back and forth. I think there are three passes. Yes, there is an o-ring at the end of the elbow joint shaft. The set screw has a flat tip. Like I said, at first glance I think maybe the barb on the shaft wore down allowing it to slide by the set screw. Will do a closer inspection when next at the boat and comfortably tied at the dock. Thank you for your input.
     


  8. JimInPB

    JimInPB

    Joined Aug 22, 2017
    579 posts, 161 likes
    Hunter 212 & 170
    us West Palm Beach
    A lot of the "round the corner" tube & bundle designs don't have the bends at the end. They are just open at both ends & gasketed plenums allow flow in & out as needed. In the universal designs, you can change the flow paths by changing gaskets &/or rotating the heads.

    Be careful that the heads & gaskets are rotated correctly when you reassemble those things.

    If your original problem was that a flat tip set screw slipped, the fix may be as easy as changing to a serrated cup point set screw to get a better bite.
     


  9. SG

    SG

    Joined Feb 11, 2017
    854 posts, 126 likes
    J/Boat J/160
    US Annapolis
    I think that the fitting is carefully designed so that when it's tightened down, it seals and the elbow is in-line with the heat exchanger.

    The heat exchanger is neither under all that much pressure, nor is the water all that hot. The hose, with it's bends, or rotation of the hose as it was clamped may have induced a long-term rotational load. That coupled with the natural vibration of your engine could have caused enough rotational force to move the fitting. Did you notice if it looks like the set screw scared the elbow as it rotated? (If if didn't scare it, if it rotated, then it wasn't being restrained. The set screw could just not have been "set" or may have been vibrated out.)

    I would make sure that when you reinstall it, you i) make sure the fitting is tight, but don't strip it; ii) the hose as connected imparts no load, iii) you might try some appropriately chose version of Locktite on the set screw; and iv) you might ask a mechanic if they'd use something on dope or sealant on the fitting [though I don't think so?]?
     


  10. MitchM

    MitchM

    Joined Jan 20, 2005
    557 posts, 67 likes
    Nauticat 321 pilothouse 32
    US Erie PA
    1/ vibration loosens set screws. tighten each year or use cold LOC TITE on the set screw. 2/ carry a tube of form-a-gasket from the auto parts store. this stuff is very useful to make a new gasket while you wait 2 months for yan mar to ship the expensive little heat exchanger gaskets from japan. arm a gasket is especially useful if you have to remove your heat exchanger end caps to clean out a piece of failed raw water impeller that migrated into the copper tubes, got stuck, and caused your engine to overheat at 11 PM on a rainy night. form a gasket got me home.
     


  11. dkerphunter

    dkerphunter

    Joined Jul 6, 2013
    34 posts, 2 likes
    Hunter 336
    CH Société Nautique de Genève
    Great suggestions... thanks!
     


  12. Chris & Lenore

    Chris & Lenore

    Joined Apr 24, 2006
    842 posts, 15 likes
    Aloha 32
    CA Toronto, Lake Ontario
    A parts manual is an excellent source of info (I have the same engine).
    The 90-degree elbow is the standard fitting and seals with an O ring and is retained by a small bolt (not a set screw) which has a gasket. It is designed to rotate i.e. not "fixed".
    The bolt does work loose with vibration so Loctite is advised.

    Yanmar part numbers are:
    O ring: 24311-000160
    Retainer bolt: 26554-050102 (it's just a M5 X 10 mm ss bolt)
    Bolt gasket: 23414-050000

    Chris
     

    Attached Files:



  13. JimInPB

    JimInPB

    Joined Aug 22, 2017
    579 posts, 161 likes
    Hunter 212 & 170
    us West Palm Beach
    The description on the drawing you posted just says "Screw M5x 10". The description does not give a UNI, DIN nor ISO number nor a description of what type of screw it is, eg. button head machine screw, set screw, hex head cap screw, etc. How is one to know what type of screw is factory correct?
     


    Last edited: Apr 7, 2018
  14. Chris & Lenore

    Chris & Lenore

    Joined Apr 24, 2006
    842 posts, 15 likes
    Aloha 32
    CA Toronto, Lake Ontario
    Because I replaced mine. It was a standard M5 (diameter/thread) and 10 mm long (which matched the description in the parts guide). It was a grade 5 and a hex bolt head.
    The local Yanmar dealer gave me the option of paying $9 for the "official" Yanmar bolt or $1 for a bulk bolt what looked exactly the same.
     


  15. JimInPB

    JimInPB

    Joined Aug 22, 2017
    579 posts, 161 likes
    Hunter 212 & 170
    us West Palm Beach


  16. Chris & Lenore

    Chris & Lenore

    Joined Apr 24, 2006
    842 posts, 15 likes
    Aloha 32
    CA Toronto, Lake Ontario
    Hardness - as identified by the attached chart. Grade 5 is the most common grade too.
    If worried just but from Yanmar..
     

    Attached Files:



  17. JimInPB

    JimInPB

    Joined Aug 22, 2017
    579 posts, 161 likes
    Hunter 212 & 170
    us West Palm Beach
    That looks to me like an SAE grade chart. Metric bolts have a different grading system, with numbers like 8.8, 10.9, etc. I am not aware of a metric grade 5 being available here in the States. Perhaps Canada is a different story. I was concerned that if it was actually grade 5, then it might not be metric. That was the only reason that I made the comment.
     


  18. Chris & Lenore

    Chris & Lenore

    Joined Apr 24, 2006
    842 posts, 15 likes
    Aloha 32
    CA Toronto, Lake Ontario
    Just go to Home Depot and get a non-stainless hex head M5 that's 10 mm long (hex head). Those are the only "fit" considerations.
    My Yanmar mechanic said there is no stress on the bolt as it just protrudes a bit into the groove in the water outlet fitting.
    He also admits to calling a metric 8.8 a grade 5 (he's American, doesn't like metric and claims they just copied the grade specs and renamed them) lol.
    Sorry for the confusion...
     



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