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  1. #1
    Cadet
    Join Date
    Jun 2011
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    15

    Post Mercury Motor Mounts

    I have a 1993, 75 Hp Mercury outboard.

    Salt water has eaten the two bottom motor mounts up that hold the drive shaft housing to the swivel bracket.

    In order to replace the bottom motor mounts it looks like I have to take the two bottom nuts off at the bottom of the swivel bracket AND the two top nuts off at the top of the swivel bracket, then separate the drive shaft housing from the swivel bracket. If that is the case, then I assume you have to remove the power head to get to the two top nuts?

    Instead of all that:

    1. Could I cut the two bottom motor mount bolts just behind the swivel bracket, and then remove the old motor mounts?

    2. Next, put the new motor mounts in place and then put the two bottom bolts in backwards? For example, slide the bolt in from the front side (i.e., slide the bolt through the swivel bracket first, then the motor mount). In the end, the bolt head would be against the swivel bracket and facing towards the bow, and the nut would be aft and against the motor mount.

    This would eliminate a tremendous amount work if doable.

    Does anyone know if this would work? Iíd sure hate to start cutting, to find a big surprise later.

    Thanks, Scott

  2. #2
    Supreme Mariner
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    On Barnegat Bay, NJ
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    Default Re: Mercury Motor Mounts

    I would think that cutting them would work. Make sure you can get all the lower cover bolts off before you begin. On my old tower, the upper mounting bolts were Grade 8 steel, 7/16" X 6", fine thread. These were difficult to find, although Merc was willing to sell them for $12ea. Obviously use nylon lock nuts.

  3. #3
    Cadet
    Join Date
    Jun 2011
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    15

    Default Re: Mercury Motor Mounts

    Thanks Chris, I guess I'll start cutting this weekend.

    Oh, yes I have one side cover bolt that's going to be a problem, but I'll drill it if I have to.

    Thanks Again, Scott

  4. #4
    Lieutenant Junior Grade
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    Default Re: Mercury Motor Mounts

    Bolts can be gotten at Fastenal. Drilling grade 8 bolts is a bad idea, they will eat your bits.

  5. #5
    Lieutenant Junior Grade
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    Dec 2002
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    pine island fl.
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    1,141

    Default Re: Mercury Motor Mounts

    Before you get started, might want to consider a plan B or what we use to call the GOBI DESERT METHOD. A saltwater motor that age, you are sure to start breaking bolts, after which you will break drill bits followed by breaking easy outs. I can certainly understand wanting to replace the motor mounts but it might be something you are better off living with. Chances are you still have a lot of metal there, you want to replace the rubber. The motor is not going to fall off the boat, just bounce around more than usual. If the motor performs to your satisfaction now, live with it.
    Last year I voluntered to try to complete a motor mount replacement on a 50 YAMAHA that someone had walked away from. Like your motor, every thing had to come apart. Just about every bolt I put a wrench on snapped off. I understood why the former guy walked away. No future there, sat down an had a heart to heart with the owner LINDA. Althought the motor was old, it was still very reliable and explained that the bolts will hold the 200 lbs, its not going to fall in the water. She saw it my way, I put it back together as best I could and she is still using it today. For the longest time, she had a big yellow rope wrapped around the motor to keep it from bouncing. Someone just recently replaced the rope with a steel cable. She takes the boat out at least 2 times a week, happy as a clam, motor is still hanging on the gill bracket. regards FRED

  6. #6
    Cadet
    Join Date
    Jun 2011
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    15

    Default Re: Mercury Motor Mounts

    Fred, I agree, donít fix it if it works.
    The problem is thereís so much up and down play that the swivel bracket tube that the shifting rod passes through is starting to bend the shifting rod.
    Like you, I see bad things happening if I take this motor apart.
    I plan to cut the two bottom 6 inch mount bolts just behind the swivel bracket, replace the mounts (this is where Iím not sure whether or not the mount is held in place by something other than the 6 inch bolt that goes through it and the side plate that has two 5/16 X 1 ľ inch bolts/screws) and put the new 6 inch bolts in backwards (i.e., with the lock nut on the drive shaft housing side vice the swivel bracket side). Iíve never replaced mounts and Iím just not sure if Iím missing something here?
    R, Scott

  7. #7
    Cadet
    Join Date
    Apr 2011
    Location
    Jacksonville, NC.
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    20

    Default Re: Mercury Motor Mounts

    I had the same problem with my '81 80HP Merc, my go to guy at one of the local repair shops told me that he usually replaces the whole drive shaft housing with a good use one (motor mounts included). In my case it works to my advantage to do that very thing since I can get the later model housing with the mounting bracket and tilt/trim and all related relays for $300.00. The replacement mounts (if I could find them - obsolete) retailed for about $45.00 each. There are also racing mounts available but they are solid aluminum and I am sure they would transfer a lot of vibration. I hope some of this is helpful.
    "Keep the Faith"
    "Still clinging to my Bible and guns"
    17' Boston Whaler 80 HP Merc
    14' Monark Jon Boat 9.8 HP Merc

  8. #8
    Rear Admiral
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    4,528

    Default Re: Mercury Motor Mounts

    1. Remove the plastic cover plates over the mounts on the mid section (two screws on the front).
    2. Remove the two mount covers (two 5/16 bolts each side).
    3. Remove the nuts from the mount bolts.
    4. Remove the mount bolts.
    5. Pry the loosened mounts out of the sockets.
    6. Order the new bolts from Merc.
    7. Order new mounts from Merc.
    8. Replace.

    If the mount on the swivel pin falls off then it's likely you have a carbon steel swivel pin and it needs to be replaced with the newer style stainless steel version.

    On second thought if that happens, junk the motor, the swivel pin cost more than that salty motor is worth.

  9. #9

    Default Re: Mercury Motor Mounts

    How do you remove the bolts? They will not slide back far enough to remove.

  10. #10
    Cadet
    Join Date
    Jun 2011
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    15

    Default Re: Mercury Motor Mounts

    Thanks to everyone for your help. The job was a success.

    The short of the story is, I cut the old motor mount bolts with a sawsall and installed the new bolts backwards (i.e., slid them in from the front with the new nuts aft). Worked like a charm and didn't have to dismantle the entire engine.

    Thanks Again, Scott

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