25 hp lower unit question

Discussion in 'Outboard Maintenance' started by love2flyfish, Mar 25, 2010.

  1. love2flyfish

    love2flyfish Well-Known Member

    So after cleaning up yesterday, I noticed a little dribble coming from the upper gear lube drain. After further inspection, whomever drained and replaced the fluid before me, never put back the upper seal. So today I went and got the seals and purchased the gear lube. When I drained the old lube it was a bit milky so I ran some ATF thru the system twice and the ATF came out milky the first time and the second semi-milky.

    So with that being said, I am thinking I might need new gear housing seals. If I just ran the motor on the wash down in the yard, is it possible for the seal to leak into the lower unit gear assembly and cause the milky color in the ATF? :-[
  2. Brett

    Brett > PRO STAFF <

    How old is the motor?

  3. love2flyfish

    love2flyfish Well-Known Member

  4. Brett

    Brett > PRO STAFF <

    6 years, might be time to pressure test the lower unit.
    Best way to check seal integrity before spending money on repairs.
  5. mark_gardner

    mark_gardner I Love microskiff.com!

    the motor probably leaked some water in it while it was sitting in the water during past boating trips, i would fill it and run it a time or two then flush again and repeat after another trip then monitor the situation, if you've got shaft seal problems then it will be obvious after several oil changes keep coming back milky. i have had 4 of these motors now and the first one i bought didnt even have oil in it :eek: the seal was in bad shape and all the lube leaked out over time :eek: no telling how long it had been run like that :-/ but the point is that i filled it and ran the heck outta that motor and never a problem. technical tip #1. always change drain plugs seals after each and every oil change ;) :cool:
  6. love2flyfish

    love2flyfish Well-Known Member

    Assuming there would be a bit of a vacuum sucking water into the lower unit if there was an issue? Any tips on how to do that test?

    SBC, I think this is the route ill go to start. I have a bunch of ATF sitting in her overnight then Ill run it once more, put in good lube, replace seals, run her once and check again. Its about time for a new impeller anyway!

    Technical Tip #2: Always check drain plug seals were installed before purchasing a motor from someone! :cool:
  7. Brett

    Brett > PRO STAFF <

    Another touch of redneck tech... ;)

  8. The_Skiff_Shop

    The_Skiff_Shop Well-Known Member

    I would try synthetic such and Mercury's or Amsoil. If you do have a leak, the synthetics have shown to minimize damage. I would flush with cheap gear case oil, then run it for a short time with synthetic and change it again checking for a "milky look". Remember, a little water goes a looooooooooooooong way and will take several flushings to remove it. I replace my lower unit oil after the first 10 hours with synthetic and stick with it.
  9. Frank_Sebastian

    Frank_Sebastian Well-Known Member

    The vacuum test is probably the most important. I would call a local shop and see what they charge for testing the lower unit. I have been lucky enough to always have been able to borrow the tester when I needed it.

    I buy and install a re-seal kit about every 4 years for my engines as a preventative measure. I change the water pump impeller every other year so when I have the lower unit off I go ahead and do the seals every other time. A lot if times I get a leak before the 4 years are up and when that happens I do the water pump at the same time.

    Best regards,
  10. aflatsnut

    aflatsnut I Love microskiff.com!

    Could be the shaft seal, allot of people just change the impeller on the waterpump and never the housing and shaft seals. This is a relatively easy fix and will give peace of mind to overheating problems.
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