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Thread: Engine mounts

  1. #1

    Engine mounts

    Morning all,Has anyone had to replace engine mounts on the C12?Engine moves about 3/4” forward when throttling up. Forward mount shows significant flex.As I understand and am subject to correction, Cat has upgraded the new mounts to a 1” stud instead of the 7/8” previously used.This will be a problem to drill out the mounts without lifting the entire engine out.Anyone been able to do this?Also the bottom nut with “set screw” is that to tension the bushing or lock the stud in place from rotating?Looking forward to some feedback

  2. #2

    Re: Engine mounts

    Are these mounts from Barry Controls?
    We have the CAT mounts made by Barry Control mounts for our 3406E's
    CAT part #140-3591 and I think, but not 100%, that the Barry # is 27458-6, 1" stud.
    A decent machine shop should be able to bore out your on engine mount to 1" from 7"8".
    They will wear out, especially if the engine mount is sitting high on the stud as there's more leverage.
    We've been thinking about replacing ours just because of hours and years except my CAT mechanic thinks they are fine.
    Apparently the biggest issue is dry rotting or deterioration of the rubber which we do not have.
    You should be able to block up the engine to remove 1 mount at a time for repair, at least that's what my CAT guy and also my alignment guy both told me.
    Probably the same procedure if the front on engine mount is 1 piece (both sides connected) just more difficult.
    That's how we did our generator mounts that did wear out, of course the genset weighs much less and isn't attached to a shaft.
    Last edited by Cricket; 11-25-2019 at 12:37 PM.
    1966 HAT50C101
    Purchased 1985 12v71Ns
    Repowered 1989 with 8v92TI
    Repowered 2001 with 3406E

  3. #3

    Re: Engine mounts

    The mounts are not from Barry. I am quite familiar with them. These are Cat mounts and for the front they are too close to the stringer to remove without lifting the entire engine out. If I have to open the hole it’s going to be with a die grinder or something similar because there is no way to get a drill straight up and down.I am not very comfortable jacking against the hull with these heavy engines to lift them enough to clear.Working out a jig to be able to brace on the stringers themselves to jack up. Not nearly enough room fwd to use an A frame and chain block.Sure looks like it’s going to be interesting.I put a photo of the amount of flex at only 1100 RPM.
    Attached Images

  4. #4

    Re: Engine mounts

    Sooo, I got the new mounts and built a jig to jack up the engine.I was absolutely horrified to find that 3 of the 4 mounts were broken about halfway through the adjusting nut under the bracket. The last one was bent and not far from breaking.What was more frightening is that there was no vibration, and two of them were polished which meant they were broken a while and just sat there vibrating on each other.Lesson learnt, don’t ignore engine mounts. Disconnect top nuts and try to turn adjusting nut and see what spins the nut or the stud.Going to check other engine today.Pics to follow.

  5. #5

    Re: Engine mounts

    Yikes that is scary! Keep us posted, if you can show one together and apart so we can see where they broke. Might be obvious to those more familiar but I can't tell exactly but I do see the bolt that looks rubbed on and mushroomed. I'm assuming that where they were broke clean through?

    I can't imagine a 400-500 hp diesel deciding to go freewheeling around under full power !
    Glad you caught it!
    1980 53' Hatteras MY, Hull # 592

    "Moon River" <-- Finally picked a name

  6. #6

    Re: Engine mounts

    Have a 1981 43 DCMY. DD 671s. Need to change out a couple of mounts and replace with Ace Mounts. Read where you made a jig to raise the engine for replacing your mounts. Would be curious hear or see what you came up with. Sounds like you might have spread the engine load across the inside of the stringers.

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