Kubota 722 pressure sending unit

Discussion in 'Catalina 30' started by uralite, May 11, 2019. Add this thread to a FAQ

  1. uralite

    uralite

    Joined Apr 26, 2018
    130 posts, 42 likes
    Catalina Catalina 30
    US Bayview
    Hey guys,

    In the process of replacing my glow plugs, I ordered a new pressure sending unit out of parts book for Kubota. This is a 3 cylinder Phasor Marine engine that I have no idea what the serial number is. I ran into this issue last year when replacing transmission. I will add some pics and looking for some opinions on what best to do. Cf0WSBnrTAaG9GwsukJ87w.jpg
    This vibrated and broke off. I can see pressure sending unit and must be temp sensor. But this was a goofy set up for sure. homemade job, with vibration not good. I bought a new temp and pressure unit combined thinking I could get rig of the copper piping.

    NpMceHPSQcmOFshbKNGQbw.jpg
    The problem, is that the pressure sending unit is so small and limited space by oil filter housing, that I had to use the elbow and piping to get combined unit to work.
    The new pressure sending unit is very small like in the top photo on the right and I see why by itself it fits in there. The bad side is the loss of engine temp sensor.

    One suggestion is to use a small hose from high pressure grease gun and lengthen the flexible connection to allow for both. My other option is to use original pressure sending unit only and forget the temp sensor. I would like to get rig of that crappy elbow conglomeration as it is what broke off and pumped oil into the bilge. If that happens underway I will have a major engine oil loss problem before I could even know what happened.

    Best suggestion. I have glow plugs going in, and I have to replace 2 seacocks yet.
     


  2. Cowpokee

    Cowpokee

    Joined Jan 8, 2015
    311 posts, 171 likes
    MacGregor 26S, Goman Express 30
    US Kerr Reservoir
    Are you sure that is a temperature sensor? More likely it is a on/off switch for the low oil pressure warning light. If it is indeed a temperature sensor, it wouldn't be the engine temperature. It would measure the oil temperature but I don't think it would be accurate. To be truly representative of the actual oil temperature, it would have to be in the flow path of the circulating oil.
     


  3. uralite

    uralite

    Joined Apr 26, 2018
    130 posts, 42 likes
    Catalina Catalina 30
    US Bayview
    Not sure, but the original oil pressure sending unit does not include that monster device. I did attach free wire to the combined unit. oil does circulate into the device. Not sure.
     


  4. LeslieTroyer

    LeslieTroyer

    Joined May 20, 2016
    2,577 posts, 1,199 likes
    Catalina 36 MK1
    US Everett, WA
    One is a switch - the other is probably for a pressure gauge. It was probably added by a previous owner. It’s a really bad idea to extend using pipe because of the vibration and torque on the extension pipe. Early Universals have a hose that runs to a manifold bolted to the transmission. I would recommend a small diameter hose connected to your T - and mount off the engine.

    Good luck removing the chunk in the block, and don’t assum it’s a NPT thread, might be metric, they are very close.
     


  5. weekendrken

    weekendrken

    Joined May 7, 2011
    137 posts, 21 likes
    Catalina 30
    3573 US Lake Norman
    What you had was the OEM low oil pressure SWITCH (not sender) and an oil pressure SENDER for an oil pressure gauge.
    The pressure sender was a PO add on.

    Your engine temp sender is elsewhere, not familiar with your block but probably at the thermostat.

    Yes, extending them like that is not a great idea.
    The newer Universal engines have a hose that terminates at a brass tee brazed to a plate that bolts to an unused engine mount hole. The tee provides a safe port to use a pressure gauge sender without adding an appendage. The oil pressure is low and can be a hose-clamp type arrangement, i.e., doesn’t need to be high-pressure hose/fittings.

    CAUTION- the Kubota engine threads are either metric (the fasteners) or JIS (the hose threads.). Japanese Industrial Standard is functionally equivalent to British Pipe Taper Thread. BPTT and JIS are not the same as (but are close to) NPT.

    The block is JIS 1/8-28 pipe thread, versus 1/8-27 NPT thread. So the OEM oil switch is 28 pitch and the pressure gauge sender and pipe tee and nipple were 27 pitch. It’s best to match threads (there are adapters available as well as NPT to BPTT nipples.). But as a practical matter if you use enough pipe dope you an thread can NPT into JIS, but might permanently “mess up” the JIS thread to NPT.

    For the best info, and best data in engine, log onto the official IC30A forum and its 1,600 experts (owners.)
    https://groups.io/g/Catalina30

    Cheers,
     


  6. weekendrken

    weekendrken

    Joined May 7, 2011
    137 posts, 21 likes
    Catalina 30
    3573 US Lake Norman
    PS. Be cautious of combined low pressure switch/pressure senders. I do panel and harness and such upgrades and the combos I found are not compatible with the typical (SW standard) pressure gauge, and will produce erroneous readings, if at all. I’ve converted the pressure switch to switch/gauge sender by the method I mentioned above.
     


  7. uralite

    uralite

    Joined Apr 26, 2018
    130 posts, 42 likes
    Catalina Catalina 30
    US Bayview
    Thanks for the replies. It’s all kinda screwed up now. When the original broke off it left some of the brass threads inside block. I used easy out and then the mechanic recut threads with npt thread cutter? Maybe? Best advice? I’m planning on putting original back in place and just leaving it as original unless there is a over riding reason to put that PO conglomeration back on. It’s designed to work with the switch only in place.
     


  8. weekendrken

    weekendrken

    Joined May 7, 2011
    137 posts, 21 likes
    Catalina 30
    3573 US Lake Norman
    Do you have an oil pressure gauge on the panel?

    It confounds me why boat mfgrs thinks it’s ok to provide an engine panel without a pressure gauge to help ID early problems yet put a temp gauge on instead of an idiot light.
     


  9. weekendrken

    weekendrken

    Joined May 7, 2011
    137 posts, 21 likes
    Catalina 30
    3573 US Lake Norman
    Here’s the bracket/tee for mounting both the pressure switch and pressure gauge sender.

    upload_2019-5-11_21-17-44.jpeg
     




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