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What is ''normal'' DD 71 series oil pressure?

Discussion in 'Technical Discussion' started by cleanslate, Jun 4, 2019.

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  1. Capt Ralph

    Capt Ralph Senior Member

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    With two wires on the alarm switch, one of those wires may go to the water temp alarm switch like on a generator.
    Your alarm system may not be as fancy as it's larger cousins systems.
  2. cleanslate

    cleanslate Senior Member

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    Sorry was busy on other stuff today .
    No I have plenty of room, just got a real close up for all you old guys on YF so you could really see it! Lol but right behind me and the camera is the Starboard engine which is an inch or two from my back side.
    Thanks a lot Capt Ralph for the clear cut identification on the two wired senders.
    Last question , there is a high pressure 1/4" blue line coming off the side of that little block eveything is going into , what's that for ?
    Last edited: Jun 7, 2019
  3. cleanslate

    cleanslate Senior Member

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    Maybe, yes I do not have any wires or senders around my secondary fuel filter.
    Btw, I only have the Racor 2020 filter then to only one DD engine filter.

    Why water temp alarm? Wouldn't that come from the water temp sender?
    Or is it really an oil temp alarm then ?
  4. Capt Ralph

    Capt Ralph Senior Member

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    The high pressure hose is from your engine block. Probably T'd in with the oil line to your turbo.
    This allows the sender assembly to be mounted where it is, or with more hose length, where ever you want.
  5. Capt Ralph

    Capt Ralph Senior Member

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    That dd engine filter for fuel? That would be your secondary fuel filter, the Racor is your primary fuel filter.
    If that dd filter for oil,,, huuummm.

    Why water temp alarm? Wouldn't that come from the water temp sender?
    Or is it really an oil temp alarm then ?[/QUOTE]
    We got the oil senders , do you have two more for the water or one?
    Like your oil sender assembly, the water temp may offer a high temp alarm that would go off around 210 - 225 *f, then a water temp sender to a temp gauge.

    Your alarm senders may be daisy chained to a single bell or buzzer just to get your attention, then look at your gauges to find the error.
  6. Capt Ralph

    Capt Ralph Senior Member

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    O K, assuming no arm switch around your secondary fuel filter, The low oil pressure alarm should come on when you turn the engine on to run, not starting or running, just on.
    When you start and it's running, the switch opens and the alarm should stop.
  7. cleanslate

    cleanslate Senior Member

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    We got the oil senders , do you have two more for the water or one?
    Like your oil sender assembly, the water temp may offer a high temp alarm that would go off around 210 - 225 *f, then a water temp sender to a temp gauge.

    Your alarm senders may be daisy chained to a single bell or buzzer just to get your attention, then look at your gauges to find the error.[/QUOTE]
    Ahh, yes I would say so. I only have one alarm per engine. Probably daisy chained....
  8. wdrzal

    wdrzal Senior Member

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    With the mass of metal spinning around (main and rod journals) how 5 psi protects & literally keeps them afloat, What RPM do you need to reach a little more respectable pressure of 20 psi ?
  9. Capt Ralph

    Capt Ralph Senior Member

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    It is oil flow that is important. PSI is the easy and cheap way to show something is there to flow.
    At 28 Gallons a minute, itsa flowing and itsa flying well.
  10. cleanslate

    cleanslate Senior Member

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    Update; well there is no fuel in the oil. That's it so far, on any updates . Lol..
    Got side tracked with removal of the original GE washer and dryer to create more storage space. Got the dryer out in one piece. But the washer was an inch to big to get past the forward stateroom door. Had to gut it, and cut it in half.
    Then the wall paper guy showed up.....that's the next project , his project .
    Yes I'll be using commercial grade vinyl. Need one bolt sized role (big #$! role) to do my 42' Ocean Sunliner.
    Hope to do the oil pressure test today.
  11. wdrzal

    wdrzal Senior Member

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    Capt Ralph, the chart in post #6 says 20 quarts pan & filter (5 gallons ) is there a dry sump for additional oil?? ? Other wise the engine is circulating its entire volume ~5 times every minute. I'm really leaning a lesson here.
  12. Capt Ralph

    Capt Ralph Senior Member

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    Lets look at what is getting oiled.
    Monster rod and crank shaft bearings. The rod bearings are 2x larger than the largest production gas engine on the road today. The bearing surface areas is quite large.
    2 cam shafts with PTO support on each end. Lots more big-wide bearings.
    Blower, each end floods in oil.
    Turbo, Has to move a river of oil to keep that center bushing/bearing floating and happy.

    But wait, there's more; All of the shafts are gear driven. The blower is gear driven. The blower drives the gear driven fuel pump. Somewhere in there is a gear driven coolant pump. Got to keep those gears happy.
    And we still send some oil up to the roller lifters for the valves and injectors.
    There is a lot of heat transfer with that oil flow also.

    These little 4 lunged monsters can make half the HP that my 12Vs make.
    I'm scared there not moving enough oil.
  13. Capt Ralph

    Capt Ralph Senior Member

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    You ask about dry sump.

    I'm going to tell you a secret. You tell anybody I'll have to beat you with a stale noodle.
    I used to build gas engines in my youth,, yes,, I am a diesel convert,, now you promised not to tell anybody...

    I did learn about oil sumps and never fell in luv with a dry sump.
    We just built larger oil pans. Baffles and trap doors.
    I can still remember the Melling oil pump part number; M77-HV.
    We modified our own pick up tube pending the sump design.
    Over sized oil filter(s) NAPA 1794.

    In a dry sump and belt driven oil pump or stock gear driven oil pump, pumps eats HP.
    When their building up pressure and fighting against the engine to pump more up stairs, HP is wasted.
    Who wants a pressure relief valve to pop, we want oil upstairs.

    We built loose engines.
    Now, lots of oil flying every where, lubing, cleaning, cooling and not taxing the oil pump.
    We had some oil pressure at idle but your not racing at idle.

    Yes, it sux when your engine blows up, but our failures were not lube issues.

    Old Detroits splash oil every where, and don't need a lot of oil pressure at idle either.
    I can relate and understood quickly without having to learn all over again when I converted.
  14. wdrzal

    wdrzal Senior Member

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    I did the same, raced everything .Its just amazing how engines spin on nothing more than a thin film of oil.
  15. cleanslate

    cleanslate Senior Member

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    Why thank you! I'm told this a lot! Lol,Lol.
    Last edited: Jun 9, 2019
  16. RT46

    RT46 Senior Member

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    Agree
  17. cleanslate

    cleanslate Senior Member

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    Actual worth while update and closure to this post;

    Port problem engine; at 70 degree F ambient temp;
    Cold start VDO gauge read 22 or so PSI. 650 RPM .
    Removed sender.
    Installed $26 Mechanical tester kit gauge read 40/43 PSI cold engine , always hunts at first cold which fluctuates the oil pressure. Whoo-Hoo. Great news!
    New VDO o-5 bar 80 psi sender installed now reads 40/43 psi on dash gauge .

    Now that I'm an expert on oil pressure testing I decided to do the starboard engine sender and gauge;
    Cold start VDO gauge read30/34 psi at 650 RPM.
    Mechanical tester read 650rpm cold 44/46 psi....
    Changing that sender out to.
    I'm happy, once in a while I catch a break!
  18. Capt Ralph

    Capt Ralph Senior Member

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    In your picture, looks like somebody had already replaced the gauge sender, probably the wrong one.
    Now, Go fishing and get those puppies hot and report hot oil pressure at idle.
  19. cleanslate

    cleanslate Senior Member

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    Will do but my ocean is not a fishing boat it's the sun liner model aft upper deck and aft queen birth and shower where the fishing cockpit would be.
    No blood and guts on my boat strictly a cruising boat.again thank you for all your help.
  20. Capt Ralph

    Capt Ralph Senior Member

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    I forgot that. Then grab da family and go for a ride.