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Big oil leak in 350 Mag MPI-gctid388739

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    Big oil leak in 350 Mag MPI-gctid388739

    Background - In 2005 I bought a 285 brand new with the 350 Mag Bravo 3 in it.

    I boat on the Chesapeake bay and the boat has always been kept in a completely enclosed boatel year around. All of my maintenance (even oil changes and winterization) is done by my marina - an authorized gold/platinum level dealer or something like that.

    I have close to 1200 hours on it (not a typo - I do alot of trolling during the spring trophy season for striped bass each year ).

    Around 700+ hours the starboard exhaust manifold developed a leak so my marina replaced both manifolds and risers and performed a 300 hour service as well.

    The problem - during the spring, I noticed a little bit of oil in the bilge and had the mechanic check it out. It was deemed "residual" since no leak could be found. I had the 300 hour service completed again a couple of weeks ago and an oil change the Wednesday before Memorial day weekend.

    I left for the weekend and on my return Monday I decided to check the bilge. Much to my dismay I saw alot of oil sloshing around in the bilge. The oil pressure and engine temp was fine the whole way home. No alarms were sounded and the boat ran well.

    The marina checked the engine later in the week and there was very little oil left in the engine (per the dipstick measurement) and they removed 3-4 quarts of oil from the bilge. No leaks could be found however.

    They are pulling the engine this week to see if they can find the source of this big leak. I was hoping for some opinions on what might be the issue here. They have hypothesized that it could be an oil pan leak or oil pan gasket. Whatever it is, something has let loose.

    Thanks in advance for comment/replies.



    Only big leak I ever had which nobody could seem to locate until it was pulled was the remote oil filter hose which stated leaking at the crimped fitting end. Replacin the hose was the fix AFTER the engine pull where it became obvious. Other areas of concern would be as your marina described and front & rear engine oil seals.
    Cheers, Hans
    2007 Carver 41 CMY
    Twin Volvo D6-370
    Montreal, Canada
    Midnight Sun I Photos


      Jim, pulling the engine is a big ticket item.

      I'd sooner see you pay up front for proper diagnostics that truly identify the location of the leak.

      The engine can be wiped down, and then run until the leak appears.

      A fresh clean white cloth can help find the location, or general area of the leak.

      Let me put it this way:

      How would feel after you paid for engine removal, and were to find that the leak was discovered to be in an area that could have been repaired without having pulled the engine??????

      Hold their feet to the fire. Make certain that the engine actually needs to be removed.

      Get this in written form as per diagnostics.

      Also.... if you do end up pulling the engine, kill several birds.

      Drive coupler for example. Check this thuroughly.

      Starter motor flywheel ring gear, for another. (this is a $22 part that requires engine removal to access the flywheel) It takes only 1 to 1-1/2 hr to install when the engine is out.

      Starter motor..... any concerns???? Inexpensive while the engine is out.

      Rick E. (aka RicardoMarine) Gresham, Oregon
      2850 Bounty Sedan Flybridge model
      Twin 280 HP 5.7's w/ Closed Cooling
      Volvo Penta DuoProp Drives
      Kohler 4 CZ Gen Set

      Please, no PMs. Ask your questions on forum.


        well...that sucks but there is something going on that alot of folks don't realize....

        let me back up a few yrs ago...we sold our boat to this nice couple and I came over to the boat and talked to them..explained some systems....explained some of my additions and showed them where the spare keys were...(I hid a set)......then went into the engine bay only to find water in the bilge up to and over the oil pan....told em to get that out or your going to have more problems than you can imagine....salt water on a stamped steel oil pan will not last long....sure nuff I get this email from him saying he was running back from someplace and the oil alarm came on..stopped the boat and looked in the engine bay and saw his 5 qts of oil floating all around......

        had to pull the engine and drive....change out the oil pan....clean out the engine bay bilge.....wasn't pretty and it cost him a couple of grand.....

        if you constantly have salt water in the engine bay and can't get it out...the oil pan will take the heat for it....

        :arr arr


          We just had friend that needed one of their engines (5.7 as well) removed due to an oil leak. At first they thought it was a rear main. It ended up being one of the hoses for the remote oil filter system. It ran behind the engine and the only way to get to it on their boat (a 30' Rinker) was to move the engine. They had coupler issues as well so the engine was removed.
          Phil, Vicky, Ashleigh & Sydney
          1998 3055 Ciera
          (yes, a 1998)
          Previous boat: 1993 3055
          Dream boat: 70' Azimut or Astondoa 72
          Sea Doo XP
          Sea Doo GTI SE
          Life is short. Boats are cool.
          The family that plays together stays together.
          Vice Commodore: Bellevue Yacht Club


            As my 2003 285 sits in the shop with the engine out...

            This just happened to me. Same story, everything fine on the last run, next time I checked a bilge full of oil and a nearly empty crank case.

            It appears to be coming from the very bottom of the oil pan, near where the remote oil change hose fits in. That's the only place there's any rust, and with a mirror on a long stick I was able to actually see oil weeping out. I assume it was coming out much faster when the engine was hot.

            I can only imagine what the haul, engine pull, repair, engine replace and re-launch will cost me.


              Well I found out the issues. Here is what they did and see as needed repairs:

              checked visually for any leak.

              Ran engine to check for leak under pressure.

              Removed drive.

              Removd engine from boat.

              Found leaking oil pan. Need to Replace.

              Found oil lines seeping. need to Replace.

              Found leaking water distribution housing. need to replace. Found major water leak at steering shaft in transom housing. Remove transom housing assembly and replace with complete housing, including all new bellows, trim cylinders, shift cable, gimbal bearing.

              Found significant play in gimbal ring at steering shaft area.

              Estimated cost with labor and parts - $4100

              The bravo transom assembly is $2275 alone - ouch!

              Oh well. This is what almost 1200 hours gets you.

              I told them to go ahead and fix it.

              Thanks for everyone's replies.