250 hp 350 engine with hydro lock on cold start

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by Griff 4, Apr 3, 2020.

  1. Griff 4

    Griff 4 New Member

    11
    May 27, 2019
    Bayliner 325
    two 350 cubic inch 250 hp Mercruiser engines Bravo II
    Hi all. My starboard engine has been showing a hydro lock while starting when cold. I had suspected exhaust manifolds and risers, so changed them. It seems to only be a small amount of water getting atop no. 1 cylinder piston only. Has anyone seen this problem before? I am sure open to suggestions! Griff
     
  2. DWABoat

    DWABoat Well-Known Member

    612
    Aug 13, 2019
    S Louisiana
    2001 280 Sundancer
    1989 220CC Cuddy Cabin
    Twin 4.3 w/Alpha Ones
    5.7 Mercruiser Alpha One
    Did you see evidence of water leaking in the exhaust port when you removed the manifold?

    May be a head gasket.
     
  3. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Heads can rust through. Vortec heads have a thin casting
     
  4. Griff 4

    Griff 4 New Member

    11
    May 27, 2019
    Bayliner 325
    two 350 cubic inch 250 hp Mercruiser engines Bravo II
    Engine is seawater cooled. General consensus seems to point towards a possible head gasket failure. I am still checking a few things before tearing down. Thanks for your advice. Griff.
     
  5. Griff 4

    Griff 4 New Member

    11
    May 27, 2019
    Bayliner 325
    two 350 cubic inch 250 hp Mercruiser engines Bravo II
    All apart now. Water inclusion in no.1 cylinder only. Could not see any head gasket smoking gun, but suspect that the intake manifold gasket was allowing water to creep into the no. 1 intake port on the cylinder head. Will clean up this mess and very carefully reassemble. Will report upon completion. Thanks for your expert advice. Griff.
     
  6. Griff 4

    Griff 4 New Member

    11
    May 27, 2019
    Bayliner 325
    two 350 cubic inch 250 hp Mercruiser engines Bravo II
    Hi all. Thanks for your input. I was expecting to find a bad head gasket. But she purrs like a kitten now and the problem was the intake manifold gasket. Coolant was slightly leaking from atop the forward left side of the intake manifold. This allowed the coolant to creep along and enter the no. 1 intact tract. There was obvious rust trails showing the seawater getting past the intake valve and filling no. 1 cylinder. On the 250HP 350 carb engine, the view of the failure point is obscured by a large coolant hose and the gear oil monitor hose.
     
    jobofly and Thornton69 like this.

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