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  1. #1

    Default "Hi, I just got a 1989 Larson

    "Hi, I just got a 1989 Larson with a 3.0 L mercrusier and I noticed that the oil in the power trim pump is very milky and the level is very low. I don't know much about boats yet but I don't think this is good!. The power trim does operate but I really think I need to drain and change this fluid. Like I said, I am new to boating, and I would like some advice on how to go about purging all of this crappy oil out of the system. Also, what oil would you recommend replacing in this pump? Any help would be much appreciated. Thank you."

  2. #2
    Join Date
    Dec 2006
    Chaumont Bay, N.y., USA

    Default "Ayuh,....... Mercruiser, o


    Mercruiser, over the years, has recommended everything from ATF to Engine Oil for the Trim system,......
    It's a pretty Simple system,+ it really doesn't matter,.....
    As long as it's an oil lighter than say 50W......

    To Purge the system,+ start over,.....
    Disconnect the lines at the bottom, outside of the transom assembley,+ lift & lower the drive by hand,... This will clear the oil from the Rams....
    Next, run the pump Up & Down alittle,+ refill it,.... Then do it again til you're getting Clean oil out of where it's disconnected,.....
    Reattach everything, Fill it Up,+ Cycle it up,& down several times to bleed it,....
    Retop off the tank,+ you're Done......."
    Any Grease is Better,... Than No grease at All....

  3. #3
    Join Date
    Aug 2006
    SW Ohio, USA

    Default "Welcome Chris: Milky oil m

    "Welcome Chris:

    Milky oil means water has infiltrated the system either thru a trim cylinder seal, a loose hydraulic hose connection or a fracture in a line. Buy a manual for your 1989 OD from this site or eBay. Factory manuals are the best in my opinion.

    Check all of the connections on the OD and hoses for leaks. If you find a loose one, it is the likely culprit. If the connections are all tight then one of the cylinders is leaking and needs replaced or rebuilt. If you have repaired the leak, you can purge the contaminated oil.

    If you have a plastic reservior you can unbolt the entire assy. and take out one screw on the bottom of the reservior to remove it and drain it. Replace the tank oil w/Merc. power trim fluid. You'll need about 2 quarts.

    Flushing bad oil: There are 2 hyd. hoses at the pump. One acts as the UP line (fluid out) while the other acts as the RETURN line (fluid in) and the OPPOSITE occurs for the DOWN movement; the hoses change jobs w/each other.

    I use a threaded nipple w/a 2' hose to use as a drain line for the UP hose then the DOWN hose (one then the other). Disconnect on of the hoses at the pump and install the drain hose inserted into a milk jug. Now run (if oil doesn't come out right away, swith the drain to the other and reconnect the 1st one) the trim pump UP; switch the hoses. REFILL RESERVIOR. Run the trim down; switch the hoses. REFILL RESERVIOR. Do this procedure a few times until the oil is clear from each hose then reconnect them and fill the reservior to the proper level.

    Someone else may give you an easier method."
    Fix minor things (replace wear items for preventative maintenance.) that cause major problems before they break.

  4. #4

    Default Thank you guys. Your help is

    Thank you guys. Your help is greatly appreciated. Thanks again.

  5. #5
    Join Date
    Feb 2006
    Arlington, VA, USA

    Default I just use ATF like Bondo ment

    I just use ATF like Bondo mentioned. (Automatic Transmission Fluid)

    Dexron Mercon III or what ever is available.

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