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Are my motor mounts good?

Discussion in 'Engines' started by Danvilletim, Jan 21, 2022.

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  1. Danvilletim, Jan 21, 2022
    #1
    Danvilletim

    Danvilletim Senior Member

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    isleton, ca
    How do you determine if motor mounts are good? We are chasing down a vibration and Running gear guys through this idea out. These are in C30s. How do you tell? What’s effort and cost to replace?
  2. rtrafford, Jan 21, 2022
    #2
    rtrafford

    rtrafford Senior Member

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    Motor mounts rarely fail other than with age, but if you have some age on them or heavy use, and if you're heading towards an alignment check and adjustment, do consider changing them if you have any question about them.
  3. Maxwell, Jan 21, 2022
    #3
    Maxwell

    Maxwell Senior Member

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    I had the motor mounts done on our Cat C12 powered boat back in 2020. We went with Isoflex mounts... parts were ~$1500, but I don't recall the labor as he was doing a lot to the boat at the time...

    The original mounts weren't completely compressed or cracking etc, but were nearing end of life. We weren't specifically trying to fix a vibration issue, however there was slightly noticeable change with the new mounts.
  4. chesapeake46, Jan 21, 2022
    #4
    chesapeake46

    chesapeake46 Senior Member

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    How many hours and what year boat, do you recall ?
  5. Maxwell, Jan 21, 2022
    #5
    Maxwell

    Maxwell Senior Member

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    2003 Tiara 42 Open... 1100ish hours when we did the motor mounts.
  6. chesapeake46, Jan 21, 2022
    #6
    chesapeake46

    chesapeake46 Senior Member

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    Thanks.
  7. Capt Ralph, Jan 21, 2022
    #7
    Capt Ralph

    Capt Ralph Senior Member

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    Like purchase surveyors, we rock the engines forward / reverse / forward at idle and in the river, the same with a lil gas after the clutches engage.
    Looking for total rocking of the engine. Old mounts look like there coming up like in your Chevy.

    Some mounts have marks that show when they have settled. Consult with the mfg of mount height of other brands.
    Mounts settle, with oil and fuel on them, settle quickly.
    A shaft alignment is fine just sitting there, apply some torque to that shaft and the motor rocks and all alignments are off.

    When in doubt, change them out.