5.0l mpi, water in oil?

Discussion in 'General Maintenance/Repair Questions' started by emunns, Jul 11, 2020.

  1. emunns

    emunns New Member

    23
    Nov 5, 2015
    Seattle
    '07 Sea Ray 240 Sundeck
    Mercruiser 5.0
    Hey all, looking for help here before I start tearing things apart.

    The boat, bought May 20th, 2020 with 695 hours on it.

    2007 SeaRay 240 Sundeck w/ 5.0L MPI mercruiser - Currently ~720hrs
    Hull Identification Number: SERV1938G607
    Motor Serial Number: OW650080
    Outdrive Serial Number: OW919318

    Maintenance we’ve done:
    -Fuel filters (5/20/20 - 695hrs)
    -IAC valve/gasket/filter (6/24/20 - 712hrs) Did this because of rough idle
    -Spark plugs (7/7/20 - 718hrs)
    -Spark plug wires (7/7/20 - 718hrs)
    -Distributer Cap & rotor (7/7/20 - 718hrs)
    -Oil change(7/8/20, hours 718hrs) old oil looked normal/unremarkable

    After doing all this maintenance we took the boat out for some WOT runs. The boat ran well at 4400rpm, ~40mph. When coming back to idle the boat stalled and motor died. It took throttle to start it back up which isn’t normal. After opening the motor hatch we saw creamy oil coming out of the Port side PCV valve/hose and the same around the fuel filter box and fuel cooler. The oil dip stick had the same tan/creamy colored oil on it and the oil level looked high. We got the boat back to our dock without any problems and the motor seemed to run fine besides a low idle(~480-520rpm) when we put in neutral. At our dock I killed the motor, let it sit for 10-15 minutes and started it up again. It took 5-10sec to fire up with a lot of neutral throttle(unusual) but then ran fine with it’s still low idle.

    Thoughts? Head gasket, manifold gasket? I’m getting ready to replace all the gaskets, head, intake, exhaust, valve...

    thank you in advance.
     

    Attached Files:

  2. Jimmy Buoy

    Jimmy Buoy Well-Known Member

    Dec 3, 2008
    Sarnia, Ontario, Canada
    340 Amberjack
    twin 8.1S 370 Hp + 4.5 Westerbeke Genset
    Sounds like you've got water entering your engine - not good. Drain the oil asap and fill with oil along with Marvel Mystery Oil to try and prevent rusting of vial engine components. Also, remove all the plugs and turn the engine over with the starter while looking for water coming out of the cylinders. You need to find where the water is entering the engine. It could be a head gasket failure or an exhaust manifold failure. My money's on the exhaust system having an internal leak, pooling water at the exhaust ports which seeps into the cylinder then past the rings into the crank case.

    If you want to rule out head gaskets just do a compression test once the plugs have been removed or a leak down test.
     
    Last edited: Jul 12, 2020
  3. emunns

    emunns New Member

    23
    Nov 5, 2015
    Seattle
    '07 Sea Ray 240 Sundeck
    Mercruiser 5.0
    Thanks Jimmy, an oil change and compression test are on my list for tomorrow. The fact that the engine is still running is good right? Not enough water in the cylinder to hydrolock or anything? would you feel safe running it after the oil change to cycle the new oil??
    I'm thinking I want to pull the risers and manifolds also to take a look. I haven't done that before though. Seems easy and straight forward. Do I need to worry about water coming in thru the exhaust when its disassembled? We don't have a trailer, we keep it in the water.
     
  4. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Hope you didn't buy a boat with a cracked block. Before you take anything apart pressure test the water side of the block and in a separate test, pressure test the exhaust manifolds.
     
  5. Spark600

    Spark600 Active Member

    152
    Dec 28, 2013
    Long Island NY
    2008 Sundancer with 496 SeaCore Bravo 3
    Kohler Generator
    Mercury dinghy
    496 SeaCore Bravo 3
    Check the oil cooler
     
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    He doesn't have 1
     
  7. emunns

    emunns New Member

    23
    Nov 5, 2015
    Seattle
    '07 Sea Ray 240 Sundeck
    Mercruiser 5.0
    scoflaw: Can you link me a "how to" on those pressure tests? I'm 99% sure it's not a cracked block. I feel it would have presented itself sooner. We ran the boat multiple times on the seller's trailer and have now put almost 30 hours on it. From all my readings I think it water leaking from the exhaust side.
     
  8. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    At the t-stat housing block the port that comes from the raw water pump and the 2 small lines that go to the exhaust manifolds. Remove the 2 senders on the t housing that have np threads. Screw a shrader valve in 1 and a pressure gauge in the other. Put about 15lbs. to it.
     
    emunns likes this.
  9. aerobat77

    aerobat77 Active Member

    605
    Aug 12, 2014
    germany
    2006 240 DA Sundancer
    5.0 MPI / Bravo III
    after draining the block into the bilge you can change manifolds and risers on the water on the 5.0 mpi . don,t ask me how i know ... lol
     
    emunns likes this.

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