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Thread: Changing lower unit fluid on Honda's

  1. #1
    Member patrickL's Avatar
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    Apr 2006
    Anchorage, AK

    Default Changing lower unit fluid on Honda's

    I'm thinking I should change out the lower unit fluid on both my 150hp main and 8hp Power Thrust motors, both Honda's. I just got the boat, its a 2006, and I don't know for sure when the last time the guy changed out the fluids. Both fluids look good so there's no worries there but I thought better be safe than sorry. Does anyone know what I am supposed to use for each motor. They look different so I am not for sure. I am also trying to avoid AMD for obvious reasons so any others suggestions would be great.

    I also have the pump from my old Mercruiser to pump the fluid up in the lower unit. This is the type that screws into the bottle of oil. Will this work on a Honda outboard?

  2. #2
    Member Rod in Wasilla's Avatar
    Join Date
    Apr 2006
    um... Wasilla...


    Go to the Honda website and download the Owner's Manual. It should tell you what kind of fluids to use.
    Quote Originally Posted by northwestalska
    ... you canít tell stories about the adventures you wished you had done!

  3. #3



    For my mains, as per my Honda owner's manual: SAE 90 hypoid gear oil with a service classification of at least GL-4. It would guess that your 8 hp kicker takes the same.

    As for the oil pump you mentioned, beats me but I bet it would. But, here's what I do to mine and the way outlined in the Honda Outboard Manual: I take out both the fill plug and the drain plug and I let it drain completely. Next I take a fresh bottle of gear oil and cut the tip of it off to the point it doesn't leak any fluid (or much) and will deliver decent volume to the lower unit. I then begin to fill the outboard through the drain hole by squeezing it (it doesn't take long) until the oil starts flowing out the fill hole. Then, with both plugs handy, I quickly cap the drain hole (you won't lose much if you're quick) and then cap the fill hole.

    While it seems strange to fill the lower unit through the drain hole, it works better then trying to fill it through the fill hole while fighting the air trying to come out while you are filling it up. I would even bet that if the air was trapped just right, you would get a false full reading. Good Luck


  4. #4


    One other suggestion I would make: Get an impact driver to loosen the drain and fill screws. Use the exact size bit so you don't ding up the slot or worse, possibly have the bit jump out of the slot and be driven into the casing. It usually only takes a couple whacks to break them loose. Inspect your o-rings (Honda uses rubber). They are usually fine to re-use but if there is any damage whatsoever, replace it. Pump your gear case oil in somewhat slowly or it will come blowing out the top before it is actually full. I have a pair of '06 Honda 150s and the manual calls for lower unit and engine oil change every 100 hours. It really isn't difficult at all and gives you the opportunity to look over other maintenence items at the same time.

  5. #5
    Member Tolman24's Avatar
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    May 2007
    Eagle River, AK


    It may be overkill but I change the lower unit fluid every fall when I winterize the boat. I do this after changing the oil, filter, and adding the fuel additives and fogging the motor. This ensures that the fluids are moisture free and ready to go next spring. Come spring I simply check the fluids, change my fuel filter and I am ready to go. I hope to get 100 hours on the motor each summer but not often a lot more. My lower unit fluids have always looked good when changing.

  6. #6
    Member chico99645's Avatar
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    Jun 2008


    When I had my honda 90, I did the same thing as Tolman24. I also put in fresh plugs after I started the motor in the spring and let it run for a while. A bit of over kill, but the Lady that bought my Boat this past spring was very impressed with my boat and maintenance. Ran the boat and motor for about 6 years and didn't loose much on the boat.

  7. #7
    New member
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    Aug 2009

    Default Changing lower unit fluid on Hondas

    Well worth it when its done. Boat just looks more in proportion when done also. Plus easier to oil shaft.I will post some pics on here tonight when i take a photo of mine that kris did for me over a year ago.Dave

  8. #8
    Member breausaw's Avatar
    Join Date
    Oct 2006


    The service manual for my 06 Honda 90 says change lower unit oil every 100 hours, for me thatís twice a year. The only pump fitting that will fit a Honda is one for a Honda, if the one you have doesnít fit just taper it off so it fits in the holeÖ.itís what I had to do. Only problem with this is you have to put the top screw in with one hand while you keep pressure on the pump nozzle. Itís always messy when you pull the nozzle and try to thread the lower screw in before too much oil comes out.
    Best way Iíve found for removing the screws is with a drag link socket from Sears.
    07 C-Dory 25 Cruiser


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