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Twin Disc MG 506 RH 1980

Discussion in 'Engines' started by cleanslate, Jun 17, 2021.

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  1. cleanslate

    cleanslate Senior Member

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    I’ve developed an issue with my starboard clutch.

    I check the oil when it’s cold and has been sitting not running it should be way up on the stick and it’s not it’s right at full.

    I start the engine up at idle check the oil again and the oil is high up on the stick and when I put it in forward my oil pressure drops down to 180-225 psi..it fluctuates at idle when I give it some throttle up to 700 or 800 RPM jumps right up to 350psi.

    reverse the pressure does not fluctuate.

    Oil is clean and fresh screen is clean and fresh I just did the work a month ago and it was doing it before I did the fresh oil and screen the screens been clean the whole time.

    Any ideas I’d appreciate it.
    Thanks
    Last edited: Jun 17, 2021
  2. Capt Ralph

    Capt Ralph Senior Member

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    Problem started after the oil change?
    What oil did you use?
    API rating?
  3. cleanslate

    cleanslate Senior Member

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    Before and since.
    Same as the engine oil 40 weight cf2.
    It went away for a little bit about 14 hours of running time but now it’s come back.

    when at operating temperature The pressure gauge dances around while in forward at 600 RPM.
    Increase RPMs to 700 or 800 and the pressure goes up to 325 or so.
    And stays steady.
  4. Capt Ralph

    Capt Ralph Senior Member

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    The oil pump constantly runs. The valve (F-N-R) directs pressure to either pack or dumps back into the sump.
    First thing to check; disconnect the shift cable and ensure the F-N-R lever on the clutch is in full F position.
    I have witnessed sloppy pressure gauges also. Are yours mechanical or electric?
    6oo in gear rpm is a bit low IMO.
    Last edited: Jun 18, 2021
  5. cleanslate

    cleanslate Senior Member

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    650 700 rpms is my idle speed.


    Everything’s mechanical.

    I will check that out and see how it does I’ll remove the linkage moving forward and reverse at the dock

    I still don’t understand why all the oil is not draining back into the sump like the other side…
  6. cleanslate

    cleanslate Senior Member

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    Correction my oil pressure gauge is electric.
    I replaced the sender around a year ago and everything was fine.
  7. Capt Ralph

    Capt Ralph Senior Member

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    Got confused.

    Can you expand on this comment? Type slow for us reading impaired.
  8. Capt Ralph

    Capt Ralph Senior Member

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    About or after this the pressure started reading funny?
  9. Capt Ralph

    Capt Ralph Senior Member

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    Lets talk about checking oil level.
    You start the motor, it settles into a nice idle. You rotate in and out of reverse and forward to fill the packs and oil cooler, then check the level at idle?
  10. cleanslate

    cleanslate Senior Member

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    Engines idle closer to 700 rpm.

    Oil pressure gauge dances around when hot, between 200 to 300 psi ..it varies in general when in forward at idle.
    Reverse seems to be steady at 325.

    Bump up the throttle to 800 or more rpms and the pressure goes up to 325 and stays stationary. This is my normal reading .

    I replaced the sender over a year ago with no problems . Old sender was shot. Not reading at all.

    I know how to check the oil.
    Running at idle , bump motor into gear forward , reverse.
    The proper way is at warm operating temperature. Which I have not done.

    I also check them when cold not running, just to see the oil color /condition.
    The oil is up past full due to the oil drainage back into the sump.
    I know the “cold not running “ mark on my dip stick.

    Now the problem motor no longer is above the full mark when she sits.
    Just at full.
    It should be above full.

    start her up and the level is now well above the full mark…
    Seems to me the oil is getting blocked up some how .
    The blockage or whatever won’t let the oil drain back into sump .
    I’ve go the correct amount of oil in .
    It’s stamped on the twin disc plate 1.3 gallons. When I change the oil, I put in one gallon and start checking from there to get to full.
    I hope this clarifies things ?
  11. cleanslate

    cleanslate Senior Member

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    All this being said, I am Busy this weekend putting my Chris-Craft Dory in the water and getting that ready.
    Time to pay attention to my bow rail before it goes bouncing off the boat into Cape May Harbor Avenue tighten it down just a bit the best I can and the fuel gauge isn’t working now.

    I must be sick in the head to have two old boats!
    o_O
  12. cleanslate

    cleanslate Senior Member

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    Update;
    Shift lever is going full travel F-N-R with or without cable connected .
    No loose cable connections etc.

    Oil is back up past full on the stick as it should be cold not running . This is my “normal” .
    I did not have time to run it yet , will report back in a few days.
  13. Capt Ralph

    Capt Ralph Senior Member

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    In your post #10, Are we just talking about one/same clutch?
    From what I can read, You say the cold (not run in a long while) level is near the full mark when it usually is taller up the dip stick but is not.
    Then after starting, The level comes up?

    Your dip stick is measuring the sump. There are no other reservoirs for oil to collect other that the working paths in the clutch.
    I do not think you have an oil filter.
    Warm oil means the clutch has been cycled. There is very little thermal expansion in oil to make large differences on the dip.

    Question, How long are you leaving the dip in the tube when checking cold?
    You should be able to read it on first pull if it has been sitting.

    First prescription; Take two shots, turn on some serious lights then practice leaving the dip in for 5 seconds after wiping clean with a towel (not an oil-sorb pad), then pull to read.
    No kidding. Leave the dip in for 5 seconds then pull to read.
    Humor me, Leave the dip in for 5 seconds then pull to read.
  14. cleanslate

    cleanslate Senior Member

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    Any twin disc transmission that I’m aware of when sitting cold , not running is up on the dipstick.

    doesn’t matter if you wait five seconds or it sits all night long or for a week oil drains back into the sump .

    I did not check it yet at idle and normal operating temperature I will do that next week. Need to get her away from the dock for that.:)
  15. Capt Ralph

    Capt Ralph Senior Member

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    You did not comment on pulling the dip and reading with out wiping cold.
    Your arguing with me with out trying.
  16. cleanslate

    cleanslate Senior Member

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    I do / did read it cold with out wiping.

    CR I’m not arguing, just not good at putting my thoughts down on e-mail paper. Or reading for that matter.

    And I do know the old time general rule ; check motors cold , transmission/clutch hot .
    But I do cold with out wipe, for a quick look over on the oil and how it looks.
  17. Capt Ralph

    Capt Ralph Senior Member

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    And your stating the level goes up when running?
  18. cleanslate

    cleanslate Senior Member

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    CR!
    Yes it was , now it’s acting right…

    I will be using the boat this weekend for the Fourth of July and why not I’ll let you know next week what happens the problem seems to come and go.

    I appreciate all your help and sorry for the confusion I’ll try and clarify things a little better on my next post.
    I can be a bit of a bull in a China shop sometimes.
  19. Capt Ralph

    Capt Ralph Senior Member

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    There was not much left in the china shop this morning. First night back on board last night, slept well but the boat missed me and told me about it this morning.
    Stb AC raw water pump not pumping, Big gen-set spit out an impeller. Yes, we miss each other.
    Kats back on board also. Think they missed da boat also.

    I keep thinking you may be just a touch over filled. That is the only way I can figure the oil level coming up. It's foaming and raising the wet spot on the dip.
    This may also cause some electric gauge bouncing. Draw off a pint and see what happens.

    Like I said before; First prescription; Take two shots,,
    I just finished mine. So, I can not stay on this forum much longer tonight.

    Think I'll go mess with the drunks on that other site.

    Stay safe & well my friend,
    rc
  20. cleanslate

    cleanslate Senior Member

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    Lol!!
    Oh Boy, yeah the boat missed you.

    Yes will do.
    I think you might be right on the overfill.

    I will check it hot this weekend and quit messing around .

    Hope your holiday trip goes well.
    Enjoy! But don’t be getting into any disagreements with the CG or the MP while enjoying your anchor ball!

    I got a good spot we always go to here in Cape May. Like I almost always due in life when other go right , I go left . I always get the same anchor spot with no agg and great views of the fire works along with minimal rocking from traffic when I go left out the CM Canal.
    There’s room to share I don’t care blabbing about it.