Outdrive Fluid Reservior Leaking From Top

Discussion in 'Gas Engines/Drives/Transmissions/Props' started by BirdieNumNum, Aug 16, 2019.

  1. BirdieNumNum

    BirdieNumNum Member

    Mar 16, 2019
    310 Sundancer 2000
    Twin 5.7 Mercruisers w/Bravo III Drives
    2000 310/5.7s/B3s. My outdrive reservoir has been leaking drastically into the bilge. The reservoir is totally wet from the top down. I removed it, cleaned it, dried it, put it back on, refilled it, took it out for about 45 minutes, came back, almost totally empty. The bottle was covered with oil, starting at the top and dripping down. Removed the top and realized there is no o-ring. Would no o-ring cause the bottle to empty out? I attached a picture.

    Attached Files:

  2. Henry Boyd

    Henry Boyd Well-Known Member GOLD Sponsor

    Apr 24, 2007
    Newburyport, on the peaceful and serene Merrimack
    ‘09 Sabre 38 Hardtop Express “Serenity”
    Volvo D6 w/IPS450 Pods
    I just looked at a spare cap I’ve been meaning to send off to the new owner of our 280. We also went through the same issue a few years back. Here is what we went through:

    Yes, there is a ring in the cap, however it is flat along the lines of a faucet washer, rather than the round cross section usually associated with an O ring.

    Could the missing washer be the cause? Possibly as the gear oil system is under positive pressure due to heat expansion of both the gear oil and trapped air inside the drive housing. You will note the top of the cap has a one way flap valve on the inside. This allows the cap to hold pressure during operation and then allow air back into the system as it cools.

    I would definitely replace the cap, and then add oil back into the drive. Personally, I would haul the boat and have the drive refilled properly by pumping oil into the drive by the bottom drain plug after draining the oil and checking for water intrusion. A drive sucking in water will blow oil out regardless of them gasket in cap because temps in the drive can exceed the boiling point of water, and water vapor/steam is a powerful force.

    Also don’t forget you need to use the synthetic gear oil for the b3.

    I can’t recall the specifics of why ours pumped gear oil out of the bottle other than it was the result of mechanical issues related to the internals of the drive. I seem recall it was the seal at the prop shafts, but may be mistaken. And like all of the repairs to the b3 it was expensive. I wish I could tell you more, but we passed all the old service records along to the new owner.


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