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Outboard Motor Repair?

Discussion in 'Boats and Motors' started by jeremytheys, Aug 25, 2004.

  1. Guys,
    I have a Mercury 25 HP outboard with a bent propeller shaft (propeller is new and fine, the shaft itself is bent). I need to replace it as it creates a very noticible wobble on the propeller when rotating by hand. I have not run the motor yet in this condition and do not intend to in order to prevent any damage.

    My question is can I replace this myself if I have a replacement shaft from Mercury? Or is this something I should leave to the experts. I've not messed around with outboard repairs too much besides making small adjustments to idle, etc.

    If I need the pros help can you please recommend anyone in teh Columbus area that can perform this work for me at a reasonable price and time period. I need to get out on the water soon after Labor Day.

  2. How could the shaft get bent and the prop remain undamaged? Are you sure it is the shaft or the prop hub? Have you removed the prop to check?

  3. The prop is not damaged because I put a new prop on. I bought the motor used from a construction company that used her pretty hard and that prop was trashed.

    I didn't realize the shaft was bent until I put a fresh prop on and spinned it and found the wobble and noticed the difference in clearance to the trim tab with the new blades.

    It is definitely the prop shaft that is bent.
  4. If your certain the prop shaft is bent, you can take it off and have a machine shop straighten it for you. You should get a manual for your motor. Not only will it help you in this repair, but in future ones as well. While your at it, it would be a good idea to change the rear bearing as well, and all seals. Do you know for sure they didn't run it with a bent shaft?
  5. No, I'm not sure they didn't run it bent. I just don't want to make things worse by doing it.

    I've got a repair manual for the motor from Mercury. I just couldn't get a good feel for how difficult this repair would be. I'm a novice to this and honestly the 240 price tag on a replacement prop shaft scared me enough to reconsider trying to replace it myself.

    I do like the idea of a machine shop straightening it out though. That can save some cash.
  6. If your unsure if you want to attempt it, you could have a repair shop take it off and still have it straightened. They could also verify if anything else is damaged.
  7. Depending on the age of the machine, the lower unit could be "welded" shut from normal corrosion. My 9.8 Merc was after 15 years and I found out when the impeller gave out and had to be replaced. Only found one shop with the know how to separate the lower unit - Shroeder's Boat Sales in Miamisburg. (937) 859-9922. I thought they were very experienced and not expensive at all. It's possible they could have used replacement part.
  8. UFM82

    UFM82 The one others want to be

    if you are not mechanically inclined and don't have any tools. I have been in a bunch over the years and some intuitive knowledge definitely helps.

    If the prop is off, you should be able to see the large nut that holds the guts in. You'll need to drop the lower unit so you can handle the deal a little easier. ( Do the waterpump while you're there.) Remove the large nut that holds the guts- it takes a spanner wrench to engage the lugs on the nut. ( The nut has the threads on the OUTSIDE of the nut.) Once that nut is removed, you can remove the carrier. Then that will give you access to the nut that holds the pinion gear on the driveshaft. Take that nut loose and remove the driveshaft- that will give you access to the rest of the gears.

    Check all the bearings for wear- if this thing was run with a bent shaft for a long time, you will have wear on them. The carrier may be worn as well- be careful about that.

    The shaft itself can be straightened if the bend isn't too bad.

    I'm typing this from memory, so it may not be 100% correct, but that is generally the procedure. It'll be stinky and greasy, but you can do it quite a bit cheaper than having it done.

  9. Wanna-be -

    My 9.8 is a 1983 model and the lower unit was removed with much problem about 3 years ago.
  10. mine is a 78 9.8 merc and i am having a tuff time finding ingnition and elec parts. have u had any trouble?
  11. I have never needed anything so far on ignition. I just took it in for a tune up because it started running rough late last year. But the problem was not iginition - just carbon build-up on the exhaust ports. I probably only put 5 hours per year on it. Call Shroeder's and see if they have parts. Bet they do.