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Life Expectancy for Cat 3412Es

Discussion in 'Engines' started by Jim Rogers, May 24, 2018.

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  1. Jim Rogers, May 24, 2018
    #1
    Jim Rogers

    Jim Rogers New Member

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    May 8, 2018
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    Location:
    Anchorage, AK
    I have done some reading on this, but was interested in getting opinions on how may hours is a lot on these motors. I have generally read that they are good, reliable motors. One of the boats I am looking at is in the 7000 hour range. I am told a large percentage of them are from running at 9kts. I am told it has been reliable and had good maintenance, and the current owner has owned it for 10+ years. I saw somewhere they I should do a blow-by test to to tell the motor's condition. If treated well and there are no issues, what is a reasonable like expectancy for this motor? What should I be looking for if I have the computer checked for usage history? If there were problems a year or two down the road, would these typically be removed and rebuilt, rebuilt in the boat, or replaced? What are some ballpark costs for a complete rebuild on a set of these motors? I am one that wants to keep things in perfect condition, not band aid repairs.
  2. Capt J, May 24, 2018
    #2
    Capt J

    Capt J Senior Member

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    It all depends on usage but generally 6-10,000 hours. However, I recently dealt with a set that 1 head dropped a valve seat but cylinder was fine the other one is missing some power somewhere but these are around 1500 hours, but lack of use. Generally they would be rebuilt in place.

    Complete rebuild $40-50k each.
  3. Capt Ralph, May 24, 2018
    #3
    Capt Ralph

    Capt Ralph Senior Member

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    I have always liked the 3412s.
    A good engine survey will offer the better picture.
  4. Pascal, May 26, 2018
    #4
    Pascal

    Pascal Senior Member

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    I put 5500 hours on a pair of 3412Es, about 60% of which at hull speed. They passed survey with flying colors, no smoke and excellent oil analysis

    They can be rebuilt in place as long as access is good and the block is fine.

    I d do a sea trial first and watch the basics starting with smoke on a cold start. Then if it s fine, do an engine survey during which the mechanic will be able to plug in ad check some history and run som tests
  5. Jim Rogers, May 26, 2018
    #5
    Jim Rogers

    Jim Rogers New Member

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    Location:
    Anchorage, AK
    Can you explain this further? I thought it was fine if they smoked when cold or under heavy load. My common rail never smokes, so I am not use to seeing this.
  6. Pascal, May 26, 2018
    #6
    Pascal

    Pascal Senior Member

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    I mean watcbing for smoke on a cold start. Depeding on outside temp they should smoke very little when started and it should clear very quickly. Being in so fl, i rarely started them in anythin under 60 deg. Above 60, by the time i d leave the helm and go aft to look for smoke, it would oretty much have dissipated. Under 60 a little more greyish smoke is ok.

    They should not smoke under load. Unless maybe the operator is heavy handed and jams the power forward. I always accelerate slowly to reduce west n tear
  7. captainwjm, May 26, 2018
    #7
    captainwjm

    captainwjm Senior member

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    Miami, FL, Cape Elizabeth, ME
    Exactly right.