TNT hydraulic swimplatform not equal lift

Discussion in 'General Maintenance/Repair Questions' started by Marc Rainaldo, Dec 2, 2020.

  1. Marc Rainaldo

    Marc Rainaldo Active Member GOLD Sponsor

    199
    Apr 18, 2019
    Netherlands
    Sea Ray 500 DA 1994
    Detroit diesel 6v92
    Hello all, since we have our 94 500da with a tntlift we had many issues. The cilinders were rotten, seals were bad etc.
    I did tried to weld the holes in the cilinders but new once came. Now the boat is tucked in we ordered new cilinders. No more leaks.

    I noticed that port side goes down and up faster then starboard. When I put a bit pressure on a side that side goes down faster or slower up.

    Probably something wrong in the motor. Is this adjustable?

    Here some pictures from motor and old en new cilinders.
    BC7243AD-6047-49B1-B5BB-A0B277D5268C.jpeg 31245D1D-51B7-4E9C-94CB-CF9F8F7CF7EB.jpeg 9B8DF458-311F-434B-9FA8-65B4212BA740.jpeg F5CFAD84-6C1F-423A-A3B4-FE107DF6BC35.jpeg C9655171-6E44-47F4-A83D-82D9E0A789AB.jpeg 239EAF45-6150-4DA5-9F1F-1C1BC4E6B6D1.jpeg
     
  2. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    It depends on the hydraulic manifold. Once the system is bled of air both hydraulic rams usually receive the same pump pressure. If that is the case for your lift, the lift will raise the side with the least resistance faster which sounds like what is happening.

    My TNT does the same thing. One side will lift faster than the other if there is no load on the platform. If you put a load on the platform.....it creates equal resistance on both rams which causes them to work .....more or less together.

    It used to drive me crazy but overtime I have gotten used to it.

    What causes one side to have more or less resistance? I would speculate that one lifting mechanism might be binding more than the other side or it could be the hydraulic cylinder itself having greater internal drag. You could swap the cylinders from side to side to see if the problem moves with the cylinder.

    I'm guessing your system is from the 1990s since I don't recognize the pump and the manifold.
     
    Marc Rainaldo likes this.
  3. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    I don't have any experience with a hydraulic platform, but trim tabs often move at different rates. The explanation I was given many years ago (and haven't found anything contradictory so far) is that it's simply due to the length of the hyd lines. The longer line will cause slower movement/slight delay.
     
    Marc Rainaldo likes this.
  4. Marc Rainaldo

    Marc Rainaldo Active Member GOLD Sponsor

    199
    Apr 18, 2019
    Netherlands
    Sea Ray 500 DA 1994
    Detroit diesel 6v92
    Thanks for the replays. The new cilinders were completely tested and should be the same. Didn’t put the platform on because of the space the boat is been tucked in.

    I tested a load (myself hanging on 1 arm) and then that arm went down faster.
    Because of the test I did by hanging, I suppose that when the platform is installed and lifting my dinghy with an outboard motor on 1 side that it’s gonna be a listing problem. 1 ram has then more resistance.
    Gonna test that in the spring. And if that happens I put my wife on the other side to equal the weight.

    Maybe take the manifold out and see what’s inside? Valve or seal problem?

    Hydraulic lines I didn’t compare.

    E0F0B73B-7147-4528-92C8-1E794BB7B463.png
     
  5. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers

    My guess is that it will be fine. It does better with weight on the platform. Also.....how did you bleed the lines of air?

    Also....hope your wife doesn't read this....most women don't like to be referred to as "ballast". ;)
     
  6. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    Before you do that swap the cylinders side to side to confirm that they are not the problem. Sometimes the new seals need a little while to break in.
     
  7. Marc Rainaldo

    Marc Rainaldo Active Member GOLD Sponsor

    199
    Apr 18, 2019
    Netherlands
    Sea Ray 500 DA 1994
    Detroit diesel 6v92
    after installing the cilinders I didn’t attached the HD lines.
    I connected empty bottles on the end of HD lines and pumped all old Wateroil out (there was water inside because of leaking from the old cilinders). Then I filled reservoir with new HD oil and pumped about 20 liter true the lines.
    I placed the platform unit in lowest position,
    Then I attached only 2 of the HD lines that raises the platform up. At top position I attached the rest of the HD lines. Then I run the platform up and down several times.

    Writing this I noticed that I did make 1 mistake. At the time I was filling the reservoir to flush the lines my wife was standing outside watching the bottles didn’t fall off. After we stopped flushing I was focused on attaching the right lines and when I took the bottles of the lines there were 2 bottles empty.
    The HD line from lock cilinder and from going down are on the same flow. The HD line from lock cilinders is shorter so that bottle was full.
    Theirfore The HD line from going down I didn’t flush good and probably also didn’t take all air out.

    First thing I will do is flush again and this time flush all HD lines and all air out.

    I am not gonna swap the cilinders again. I did this for couple times and always alone. It isn’t a nice job when you are alone. After that job I am always tired. Frame pieces are heavy.

    My wife laughed about the ballast option. She only weight 55 kg so that’s oké.

    On the pump are also 2 red rotary knobs. What they do?
    Behind the rotary knobs there are 4 rotary things (srry don’t know the English name). They are tight with a nut. What they do?
     
  8. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    Can you post a couple of closer pictures of the valves?
     
  9. Marc Rainaldo

    Marc Rainaldo Active Member GOLD Sponsor

    199
    Apr 18, 2019
    Netherlands
    Sea Ray 500 DA 1994
    Detroit diesel 6v92
    In a week or two I go work on boat again and can make closer pictures. Bit busy on work. TNT lift emailed me this picture before. It’s not exactly the same as mine and although it’s written what it is , I have no clue what will happen when I turn.
    82E70250-3563-43AB-92F2-A1796D59C44F.png
     
  10. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    The two red knobs correspond to the Up valve and the Down valve. The only time you would ever turn those valves is if the electric pump fails and you have to use the manual pump lever at the front of the manifold (above the pressure gauge) to move the platform. I believe screwing a red knob down will open the corresponding valve. Then you would manually pump the system to raise or lower the platform. Once the platform is in the position you want....you would close the valve and the platform would stay put.

    A good idea in theory but useless if a cylinder or a hose develops a leak. The only time those valves are useful is if the electric pump fails.

    I would get the air out of the system before I would touch anything on that manifold.
     
    Last edited: Dec 4, 2020
    Marc Rainaldo likes this.
  11. Marc Rainaldo

    Marc Rainaldo Active Member GOLD Sponsor

    199
    Apr 18, 2019
    Netherlands
    Sea Ray 500 DA 1994
    Detroit diesel 6v92
    Really appreciate your effort and thoughts John. Your explanation of the two red knobs make sense.

    I also agree with you that first all the air have to go out of the system. Working on the manifold can be done when the boat is back in the water with the platform installed.

    I come back with a short update when I flushed the HD lines and get the air out. After that we can only wait till the winter is gone to preform more tests.
     
    carterchapman and PlayDate like this.

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