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  1. #1

    Default 1987 Mercury 70 hp trim/tilt – Rebuild or Replace or Upgrade

    I posted this on another forum... Lots of views - no opinions. Hopefully, I'll have better luck here.

    My 1987 Mercury 70 HP seal blew out on the top of center cylinder. It was leaking down before, but now it will not raise the motor at all.

    Questions:
    1) Should I have someone rebuild it? If so, what should I expect to pay? Who would you recommend do it?

    2) Should I try buya new one? (This seems cost prohibitive, but there are some parts that need to be OEM regardless of the $.)

    3) Should I try to find a rebuilt one? If so, what should I expect to pay? Who would you recommend I get it from?

    4) For either of the 3 questions above, I’ll need to remove the Mercury Tilt/Trim unit. How difficult is it to remove? (As far as corrosion goes, the motor appears to be in great sahpe especially for it's age. I was hoping this would not be impossible to remove.)

    5) Should I upgrade to an aftermarket Tilt/Trim unit? For example, the CMC PT-130 looks like a good option. My thinking is that I can get the performance gains of static jack plate and have completely new parts. It seems to me that I could remove the Mercury T/T [to save weight] and then bolt the raised mid-section to the transom plate so that the motor won’t spring up when in reverse. (There appears to be bolt holes where the casting of both sections line up and could be bolted together.)


    THANKS!

  2. #2
    Join Date
    Sep 2010
    Location
    ontario
    Posts
    9,793

    Default Re: 1987 Mercury 70 hp trim/tilt – Rebuild or Replace or Upgrade

    The repair kit for the tilt cylinder is less than $75 and it is not rocket science to install.----Hopefully all the bolts come out OK.--If you have time than you can do this yourself.

  3. #3
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    8,505

    Default Re: 1987 Mercury 70 hp trim/tilt – Rebuild or Replace or Upgrade

    Ditto the above - if you have any mechanical inclination you could rebuild it yourself. I expect a dealer would bill at least two hours for this so if you go that route you can figure on upwards of 300 bucks for parts/labour.

    Would I personally upgrade to the jackplate with T/T - not on a 70 horse. A plate will allow you to "tweak" both the top speed and drag (gas mileage) of the motor, but when I say "tweak" I'm talking about fairly small numbers - definitely not the impression that the glossy ads would have you believe.

    I use an adjustable jack (6" setback) on my 140 and by fiddling around with the adjustments and checking the results with a fuel flow meter I was able to save .6 gph (couldn't detect a noticeable gain in speed - as the "test day" progressed the speed varied by maybe 1 mph on the gps when testing for optimal gph at cruise speed). Since most boats see far less than even 50 hours use a year it would take quite a few years before you recover the 650 dollar list price of the unit you note.

    If you want to fiddle with a jack, get a basic, manually adjustable unit (widely available for 150 bucks or less if you shop the discount places) - if you run the motor alot (like 100 hours a year), it will pay for itself in 2 or 3 seasons. If you have visions of getting more speed, then shop for a larger motor. If you squeeze 1 or 2 more mph out a jack (with a 70 horse) you would be doing very well.
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

  4. #4

    Default Re: 1987 Mercury 70 hp trim/tilt – Rebuild or Replace or Upgrade

    You guys are quick. Thanks for help.

    I do have a good bit of mechanical experience; however, I am a much better "parts changer" than craftsman... I am going to put my FSM to work and at least attempt the rebuild. My gearhead buddy at work recommended the same.

    The worse I can do is loose the $75 in the cost of the rebuild. The engine corrosion is minimal, so hopefully the pieces will come apart without too much trouble. Any tips on the removal of the pins and shafts would be appreciated.
    Last edited by JP 3; 08-26-2013 at 03:07 PM.

  5. #5
    Join Date
    May 2007
    Location
    Inverary, Ontario, Canada - The Great White North Eh!
    Posts
    8,505

    Default Re: 1987 Mercury 70 hp trim/tilt – Rebuild or Replace or Upgrade

    If the pins are "frozen" in I usually hit them with some liquid wrench (or like), leave them over night then take a brass drift and a mallet to them.

    If that still doesn't persuade them to move I get the propane torch on them, heat them up and then spray them with a squirt bottle of cold water. That will sometimes break the "corrosion weld". The heat expands the metal (a bit and at different rates, it's just propane) and then quickly cooling with the water causes contraction which will most times break the pin (steel) free from the mount (aluminum) - again a good whack with a mallet/drift usually knocks it out.
    Graham

    A "professional" is someone who gets paid for their work - it doesn't necessarily mean they are good at it :)

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