Replacing a prop shaft on 9.9 Yamaha

Rhett Owens

Rhett Owens

Active member
I bent my prop shaft and water is getting into the lower unit...called and got estimate $450 AAAAAAAAAAHHHHHH.

Has anybody replaced the prop shaft? How hard is it? Any special tools? Can I run it as is?
 
You have to take all the guts out of the lower unit. The only specialized tool I would recommend is a factory manual for your motor...not a Seloc or Chiltons. You will probably have to replace all the seals too. You could probably keep using it if you drained and refilled the oil every time but in the short run, you will mess up the other stuff in there too.Are you sure the propshaft is bent? If it's not real bad you should be able to have it straightened at a machine shop.
 
Welllllll....you have to take the lower unit off, the driveshaft has to come out,shift shaft, the big nut thing behind the prop that the shaft goes through has to come out (takes a tool or hillbilly engineerin) then I'm lost on a yammy. On a Johnson you have to take out a screw that looks like one of the drain screws(never take it out by the way if you omc owners are changing oil). You HAVE to get a manual.It comes apart in sequence... Ask your dealer how much he would charge to take it out and put it back together with you straightening the shaft yourself. go to www.kencook.com and see if they have a manual for your specific motor, you should have one anyway if you are going to do more than change oil or spark plugs.
 
Rhett, what year is your motor? If you can get a good used lower, the removal and replacement is a 1 hour job. To tear down and rebuild is a headache. Been there and done that.

To replace, you would shift into neutral, remove the LU, remove water pump cover and replace impeller while you have the replacement open (as you want to do this every so often), slide drive shaft of replacement up into housing and powerhead, bolt up and go. As others have recommended, a manual is a must as they may want you to coat the mating surfaces with silicone or there may be some other small tricks. But basically, thats it.
 
Rhett, Lee is right on with his advice but I have to toss a bit into the mix. I was going to straighten a prop shaft on a 90 hp Yamaha until we priced out a new one. I forget the price but it was a total no brainer to use a new one. Your call, but at least price one out you may be surprised. If you want to bring it to Mpls./St. Paul my students are doing lower units right now. I don't know that motor off the top of my head but a teardown with the right (factory) manual is not a big deal. If you don't have a water leak it should be a out with the old in with the new. Don't let it rust or freeze. Good Luck and keep us posted. ? welcome.
 
I understand. The prop shaft is in the lower unit and as he quoted the price for repair of the prop shaft alone, replacing the whole lower with a good used could be 1/2 the price and is a relatively easy job. That is why I recommended replacing the whole thing as opposed to that one part with a lot of work.
 
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