Cummins Marine Diesel Repower Specialists › Forums › Cummins Marine Engines › 1999 6BTA blow by

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  • November 5, 2021 at 6:40 am #122671

    Thomas whittemore
    Participant

    Have a 1999 Tiara 3100 with twin Cummins 6BTAs. Starboard engine is original 1998 version, port a 2015 version. Do not know history behind newer engine. It does not smoke like older engine at idle.
    Only 700 hours on older engine. Turns up to 3150 WOT neutral. 2650 WOT under load. Getting new props to allow turn up to 2900. Do not know why wrong pitch props on boat. Cannot re-pitch to what is needed.
    Installed envirovent on starboard engine yet top filter clogs with oil pretty fast. White smoke seaps out at idle. Putting hand over oil fill port at idle feels no real suction or push.
    Appears that boat was used by a realtor group for years as means to view waterfront property. Assume a lot of low speed ops that loaded up engine. Older starboard engine may be coked up, rings fouled, injectors fouled, valves off, etc.
    Looking for ideas to remedy. Assume I should (in this order) adjust valves, clean/adjust injectors, use Marvel top oil to clean rings.

    Any help appreciated.

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  • November 7, 2021 at 5:53 am #122730

    Thomas whittemore
    Participant

    Port turbo was found seized during survey when purchased boat in Feb 2021. It was rebuilt before sale. I was told that starboard turbo was rebuilt two years before that. Stb spun freely when surveyed in Feb 21. I assume that the exhaust setup is the standard for the Tiara 3100 Open, a large volume production boat. Prior owner replaced exhaust elbows and tubing sometime before I purchased boat. No real maintenance records were found.
    With the newer elbows I doubt they are leaking at internals. Could be some splash back at low speed. Not much room to raise or extend elbows after turbo due to close quarters with hatch closed.

    November 6, 2021 at 3:01 pm #122721

    donald roth
    Participant
    Vessel Name: Paumalu
    Engines: Cummins 6BT 180 hp
    Location: where the fish are!
    Country: United States

    Looks like exhaust elbow and turbo have been replaced, any idea why and when?
    Canā€™t tell from your pics, but my first guess would be an incorrectly engineered exhaust system.

    Designing a Marine Exhaust System

    November 6, 2021 at 9:21 am #122716

    Thomas whittemore
    Participant

    port SN 60280671. Starboard SN 45682014. Engine Pictures attached. Also included pics of exhaust setup. Look OK??

    November 5, 2021 at 4:11 pm #122710

    Tony Athens
    Moderator
    Vessel Name: Local Banks
    Engines: QSB 6.7 550 HP
    Location: Oxnard, CA
    Country: USA

    Post good pics of your engines showing everthing and engine serial numbers

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