Hydraulic Steering on Mercury Inline Sixes (1970s)

Discussion in 'Engine Questions' started by David Serafin, Nov 12, 2017.

  1. David Serafin

    David Serafin Hydrodyner

    Joined:
    Oct 7, 2014
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    29
    Boat Model and Year:
    1969 18' Twin Rig
    Has anyone installed a hydraulic steering system on Mercury inline sixes? I was intending to use a SeaStar front mount cylinder on my '70 twin 1350s, but I don't see anything pre 1984 on the application chart.

    I'm trying to verify the dimensions before finishing my splash well/transom area.

    Thanks,
    Dave
     
  2. David Serafin

    David Serafin Hydrodyner

    Joined:
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    Boat Model and Year:
    1969 18' Twin Rig
    I guess it's a moot point, as the '18 splash well doesn't meet the width requirements for twins with the SeaStar. Any other ideas?
     
  3. ski38off

    ski38off Photo of the Month

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    Boat Model and Year:
    1976 18', 200 hp, and 1977 18' 150 hp twin rig
    Ski Team:
    Lake Shelby Skiers
    It can be done. I have a pair of 150 hp straight 6's on a 1977 18'. If you keep the original clamp brackets, the engines will only tilt up about 15 degrees. I ended up swapping my clamp brackets for the newer style. The ones with all the hydraulics on the outside of the transom. One was off a 115 hp 4 cylinder and the other was off a 150 hp V6. They tilt at different speeds which sucks but they were both cheap. I can send pictures of the final install if you like.
     

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  4. David Serafin

    David Serafin Hydrodyner

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    Boat Model and Year:
    1969 18' Twin Rig
    Thank you! The final install pictures would be great. My 135s have no hydraulics, they are manual tilt. I wouldn't mind adding power trim/tilt. Now for 20 questions:
    1. I assume that you used the front mount SeaStar cylinder. Which model?
    2. Was the tilt limitation due to interference with the clamp screws?
    3. Are the replacement brackets power trim, tilt or both?
    4. Apparently the same clamp brackets fit a variety of models. Did your research discover the full range that would work?
    5. Tech support at SeaStar Solutions said the front mount won't work with my '70 motors because the tillers have a single hole on the end. Did your later motors have additional holes, or did you modify them? It looks like I can remove them and modify or replace, especially if I replace the clamp brackets.
    6. Did you have to modify the splash well? It doesn't meet the dimensions in the installation manual, but my measurements show it will fit.

    I have never done anything like this, and would really appreciate any tips on the steering and on rigging twins in general.

    Thanks again,
    Dave
     
  5. ski38off

    ski38off Photo of the Month

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    Boat Model and Year:
    1976 18', 200 hp, and 1977 18' 150 hp twin rig
    Ski Team:
    Lake Shelby Skiers
    Dave, if you have never done anything like this, you will have a hard time. It took some lathe work to get the clamp brackets to fit the motors, the bar between the motors was custom, the hydraulic cylinder mount was kind of custom. Where are you located?
    1- I used the off brand front mount cylinder, can't remember the name right now.
    2- I cut the clamp screws off and welded nuts on to tighten and the cylinder still hit, so yes, it hits the screws.
    3- both trim and tilt
    4-There are subtle differences in clamp brackets for different years, size engines. I believe the 4 cylinder 115 bracket fit without modification, the 150 hp V6 bracket needed some special bushings.
    5- The single hole mount was not a problem. One bolt goes through the cylinder arm, tiller handle, and cross over bar.
    6- Splash well did not need modification, although it was tight.
    Here are pictures of the original install with the stock trim - tilt external cylinders. I'll get some pictures of the revised system soon.
    Mike
     

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  6. ski38off

    ski38off Photo of the Month

    Joined:
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    Boat Model and Year:
    1976 18', 200 hp, and 1977 18' 150 hp twin rig
    Ski Team:
    Lake Shelby Skiers
    Here are some pictures of the newer style clamp brackets. 20171122_092628.jpg
     

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  7. David Serafin

    David Serafin Hydrodyner

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    Boat Model and Year:
    1969 18' Twin Rig
    Mike,
    Wow, great pictures! What a beautiful installation. I hadn't seen the uflex cylinder before. It looks like the better option due to the connection. I have some more questions, but I'm not up to twenty yet.
    1. Did you use their helm also?
    2. The new transom clamps would solve another issue - the thickness of my rebuilt transom is pushing the limit of the clamps. I want to add plates, but it's iffy. What are yours made of? Are they front and back, or one that folds over?
    3. What is the centerline spacing between your motors? What height are they mounted? Mine had 3/8 to 1/2" spacers above the transom.

    I'm sorry about all the questions. I imagine the info was probably posted when you did it. I do intend to get help rigging the engines. I live in the Atlanta, GA area. I'm looking for someone with some expertise.

    Thank you for all the help!
    Dave
     
  8. ski38off

    ski38off Photo of the Month

    Joined:
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    Boat Model and Year:
    1976 18', 200 hp, and 1977 18' 150 hp twin rig
    Ski Team:
    Lake Shelby Skiers
    1 It is a Teleflex helm.
    2- I have 1/4" aluminum plates on front and back, nothing on top.
    3- spacing was set using the original tilt cylinders and clamp brackets. I'll get a measurement next time out in the shop. They are mounted about an inch high. Could go another inch up.
     

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  9. jim

    jim Hydrodyne 18 Specialist

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    Location:
    FL
    Boat Model and Year:
    77 Dyne 18 I/O converted to Outboard
    My transom plate folds over the top. I think this is a bad idea, especially with twins. It puts extra strain on the transom at the right and left edge of the plates. It has worked for my installation, I think because I have one 150hp installed and my boat is used primarily for low speed work.
    I have seen twin installations that cracked the transom.
     
  10. ski38off

    ski38off Photo of the Month

    Joined:
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    Messages:
    56
    Boat Model and Year:
    1976 18', 200 hp, and 1977 18' 150 hp twin rig
    Ski Team:
    Lake Shelby Skiers
    Engines are spaced 17" apart, center to center. I have been running for 4 years and no cracking, but it is a brand new transom with extra fiberglass. A weak transom with plates would stress crack at the corners of the splash well.
     

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