Merc 496 Stuck Valve

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by Ryanm51981, Nov 17, 2019.

  1. Ryanm51981

    Ryanm51981 Member

    Apr 10, 2012
    Peconic Bay NY
    2006 Sea Ray 290 ---- SOLD
    2006 380 Sundancer - current
    8.1 Mercs v drives
    I recently noticed that I was losing about 180 RPMS when throttle was wide open on my merc 496 with 475 hours. Long story short had my mechanic come down and he did a compression check and said that I had a valve that was sticking . He is recommended redoing the head .
    Is there any chance this problem will just work itself out over time ? From what I’ve heard a lot of motors start up in the spring time with valves sticking and after The motor warms up it’s fine .
  2. hottoddie

    hottoddie Well-Known Member

    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 EC
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin 546s Plotter
    454 Crusaders
    I would add a pint Mystery Oil to the crankcase and a pint to the fuel tank as well. Given the time of year in NY you will probably need to wait until next spring. Give the boat a couple of good runs and recheck compression while still warm.
  3. outobie

    outobie Member

    Apr 26, 2019
    2006 340 DA Sportsman
    87 Tiara 270...For Sale
    8.1 Horizon Vdrive,
    Twin Mercruiser 5.7 alpha 1 gen2
    just curious...why were you running your motors at WOT? is that something you normally do? or were you doing some sort of sea trial/test? I just picked up a 340 in July with the 8.1 Vdrives and the surveyor ran it at WOT for about 2 min during the test but that was the only time.

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