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OMC Cobra lower unit leaking gear oil

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  • OMC Cobra lower unit leaking gear oil

    HI,I am a new user to this forum, but have been active in several Ford related forums over several years. The reason I am here is because I have a problem I need some help with (sounds like an intro to AA doesn't it). I have a 1988 VIP Valiant with a OMC 4.3L and Cobra drive. I bought it last summer and the boat is in exceptional shape for it's age. I looked at boats 10+ years newer than this one that were in much worse shape.I had it serviced a few months ago with the service center greasing the u-joints in the outdrive and filling it back up with fresh synthetic gear lube. After taking the boat out about 6 times this summer, I noticed that when I drop the trim to drain the excess water out of the lower unit, I get fresh gear lube with it as well, but not everytime. I constantly check the level which is OK, so what looks like a lot of oil on the ground must not be very much at all.I pulled the prop to gain visual access and I could see where it may be leaking from that last seal that you can see on the prop shaft. My OMC service manual shows two seals right there back to back. The only other place I can see for it to leak is from the o-ring where the inner housing mates to the lower unit. I made sure the 4 bolts that hold this were snug.Any ideas on where this leak could be coming from? I have never hit anything on the lake. The only other thing that concerns me is that sometimes at idle speed (speed just after the drive is enguaged, I hear the drive popping like it is trying to disenguage. Don't know if this is related or normal or what. It also does not seem to matter how much I drive the boat. I spent hours pulling skiers two weeks ago and no oil leaked, but I drove it for maybe 1 hour last weekend and it leaked.Sorry for the long post.Thanks,Mike

  • #2
    Re: OMC Cobra lower unit leaking gear oil

    Well,After performing a pressure test, I can tell that the bearing housing in the lower unit is leaking at the o-ring seal where the 4 bolts are that hold it to the lower unit. It looks like it may even be cracked. The manual says that you must pull the lower unit to remove this piece, but after reading the manual and looking at it, I don't see any reason it can't be removed with the stern drive on the boat. Is this true?------------------Michael BradburnAMSOIL Dealer - 1988http://www.mcbproducts.net1988 VIP Valiant 175HP


    • #3
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      Re: OMC Cobra lower unit leaking gear oil

      True, bearing housing should come out with removing gear case. the 4 bolts have o-ring on them. Shift cable to gear case should be red.Try someone there should direct you to site about shift cable.
      Help somebody every day, if you can.