2001 F100, need help determining if lower unit is FAILING!

[ruggybuggy]

I recently bought a used F100 from a local marine. The motor looked great but when he removed it from the stand I notice a new skeg had been welded back on the lower unit. The motor had a stainless steel prop on it and I knew that when they hit damage could be done to the lower unit. The marine owner assured me that the lower unit was fine and offered a two month warrany. The gear oil was changed and the motor was installed on the boat. I used the motor for about 15 hours and decided to use a high quality synthetic gear oil. When I removed the magnetic plug the end was covered with metal particals, not large peices, just small "fur" that spread out to completely cover the end of my thumb. I refilled the lower unit and ran it for another 6 hours and checked the magnet and discovered more "fur", but considerable less that the fist time. I refilled again and ran the motor for about 1 hour, removed the plug and found a trace of fur. The lower unit has no water in it and shift fine. Should I be worry about the "fur" and get the marina to yank it apart or is this normal for Yamaha. I had a Suzuki before this one and after a season I would never see anything on the magnet.

Sorry for the long post.
Thanks

[Ken]

jrobert,
I would be more concerned about the prop shaft being bent - check it very carefully. If it is not "out of round", then I would not worry about the lower unit since it is shifting fine and, I assume, you hear no abnormal sound, like grinding, coming from the gearcase area.
Usually when something is hit hard enough to break or bend the skeg, then the prop can also get hit and the shaft can get bent - also, the gear housing can crack - but this leads to leakage of oil and intrusion of water - inspect the lower unit gear housing very carefully, especially around the prop shaft area where the thrust washer is.
You might voice your concern to the dealer and try to get him to extend the warranty on the lower unit.
Good luck [img]smile.gif[/img] ,
Ken K

[ruggybuggy]

The prop shaft is OK and there is no water in the oil. It shifts fine with no noise. The only probem is the amount of "fir" on the magnet which seems to accumulate to quickly. I did notice that the prop shaft has a slight vertical movement. I check a few used Yamahas at the marina and some had this play and some didn't so I wasn't to concerned. The dealer won't extend the 2 month warranty. I purchase the F100 as used and only got the warranty because of the concern that the lower unit might have a problem. I have about 5 more weeks of warranty left and if there is a problem would much rather have the dealer pay for it but I don't want to tear into a good lower unit either.

Thanks
Dave

[Ken]

Dave (sorry about "jrobert"),
Since the "fur" you are seeing on the magnet is considerably less each time you check it, I would not tear down the lower unit - you probably could not get the dealer to do it anyway since the lower unit is operating fine.
The lower unit may have been torn down before you bought it and parts replaced - the "fur" could be from prior damage.
Put as much running time on the motor as you can before the warranty runs out - if the "fur" continues to appear, press the dealer for a teardown.
Good luck [img]smile.gif[/img] ,
Ken K

[ruggybuggy]

Thanks Ken! I will try to get as many hours on it as I can and if the "fur" continues I'll get the dealer to take it apart. I spoke to him about it and he agreed to have a look at it. You might be right about the lower unit being disassemble previously because I notice marks on the lower case next to the bolt that hold the lower unit on and the speedo water tube is disconnected. Right now is prime fishing time on Lake of the Woods and I would hate not having the boat.

Thanks for the help,
Dave