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CAT 3208 TA's Smoking

Discussion in 'Engines' started by Merlinj79, Feb 6, 2026 at 2:07 AM.

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  1. Merlinj79, Feb 6, 2026 at 2:07 AM
    #1
    Merlinj79

    Merlinj79 New Member

    Joined:
    Jan 17, 2024
    Messages:
    20
    Location:
    San Diego
    375HP. About 1000 hours each. Boat is 1994 Ocean Alexander 46.

    A fair amount of greyish white smoke above 2100 rpm, just a little in the high teens. None at lower rpms.

    Both engines smoke the same, both start fine, run fine with WOT rpm around 2600-ish. I suspect the rpm is lower than 2800 due to the props, but not certain.

    Rpm was the same on the purchase survey, but I'm pretty sure they weren't smoking then (early 2024).

    I mostly drive around the bay at 1000-1200 RPM, occasional short, faster runs.

    The fuel is from last summer, 50% left with stabilizer added. I just don't burn that much cruising around the bay at sunset.

    Need to get the aftercoolers checked, but an oil sample two years ago was normal, no Sodium (my tech forgot to do the last oil sample).

    I took it out and ran it hard for about 30 minutes today, did seem to improve a little after that.

    I don't have any diesel experience other than owning this boat for a couple years. Any idea what might cause the smoke? Looking for a sanity check before I get a pro involved.
  2. Capt J, Feb 6, 2026 at 7:35 AM
    #2
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,797
    Location:
    Fort Lauderdale
    How many hours at 1000-1200 rpms do you run, before running it at cruising speed? Having the boat over propped by 200 rpms is a big problem, why wasn't that remedied when you bought it? How clean is your bottom and running gear? When was the last time the engines were serviced and what was done?
    Last edited: Feb 6, 2026 at 7:59 AM
    Capt Ralph likes this.
  3. Merlinj79, Feb 6, 2026 at 10:56 AM
    #3
    Merlinj79

    Merlinj79 New Member

    Joined:
    Jan 17, 2024
    Messages:
    20
    Location:
    San Diego
    Routine service (fluids & filters) only in the two years I've owned it, neither the surveyor nor management company seemed concerned. I haven't discussed the smoke yet, trying to get an idea what the issue might be and whether I should find a cat-specific tech (hard to get service onsite at my marina due to their insurance rules, limited options).

    One engine had an injector pump rebuilt about three years ago.

    Hull and gear should be clean, I have routine diver service and he's good about sending me pics if he finds anything amiss. Hauled, soda-blasted and painted less than two years ago, props were tuned up too.

    Potential over-prop is something I've learned about since it was hauled, it's my first boat aside from a seadoo and years of submarines in the Navy. So diesel is what's new to me, I was on the nuke side in that Navy.

    Usually do afternoon sunset cruises for a couple hours at 1000-1200, with maybe 5-10 minutes at higher rpm on average, but not usually above 2000rpm.
  4. Capt J, Feb 6, 2026 at 9:20 PM
    #4
    Capt J

    Capt J Senior Member

    Joined:
    Jul 11, 2005
    Messages:
    14,797
    Location:
    Fort Lauderdale
    You need to cruise it at cruise rpms for 30 mins about every 4-6 hours. Props need to be cut, CAT dealer has insurance. I'm sure of that. Smoke might mean engines need new nozzles and injector pump rebuilt or who knows, could just be dirty air filters.
  5. Capt Ralph, Feb 6, 2026 at 10:02 PM
    #5
    Capt Ralph

    Capt Ralph Senior Member

    Joined:
    Sep 8, 2004
    Messages:
    14,193
    Location:
    Satsuma, FL
    In the cold air, dirty steam (smoke) may be more obvious.

    Sometimes it takes more that a couple of minutes to blow the junk out. How about 15-30 minutes under a good (90%+) load.
    Get those temps and really heat up the exhaust system and blow that gunk out well.

    After some good runs, check out the smoke.
    Here in the swamps, we put our face in the exhaust to determine how much un-burnt fuel is actually in the smoke.
    If it burns your eyes, it's fuel. Overloaded, poor turbo action, clogged air filters, leaking injector(s).

    But before you can worry about any of this and end up on your knees (or bent over); Service the engines including fresh air, case and fuel filters.
    Correct oil and oil filters.
    Do you have factory prop spec? Ensure you make RPM per factory spec/HP.

    Old diesels don't like to idle around for long periods. It takes 10 minutes for our ole engines to start to clear up, come to temperature and start to preform after a day of fast idling around.

    Lets get some oil lab reports posted and keep them coming.

    Take two aspirin after this and call us back.
    Last edited: Feb 6, 2026 at 10:09 PM