I found out from a boat mechanic that I had a bent prop shaft.  He told me that I needed to replace the lower unit.  I asked him "what would happen if I didn't replace it?"  He told me that I could probably go for awhile, but sooner or later the lower unit would quit on me.

My motor is a 1990 Suzuki DT85 and not worth the $1,000 it would have cost me to get the lower unit replaced.  Therefore, I elected to keep using it until something happened.  Well...something happened.

I was out on the lake going about 25-30 mph when I started to hear sort of a steady, rythmic, banging sound.  It wasn't real noticable at first, it just sounded like my motor was getting louder.  Soon after that, I heard (and felt) a very loud series of metallic bangs and the boat slowed to a stop, but the motor was still running.  I shut the motor off and limped home on the trolling motor.

When I got out of the water, I noticed that I could not turn the prop by hand in either direction.  There was no noticable external damage to the motor, but I haven't taken anything apart yet.  Here are my questions:

1.  What do you think happened?  My guess is that the lower unit is shot, but I have no idea how extensive the damage may be.

2.  If it is the lower unit, how hard is it to replace it.  I can get a fully assembled lower unit on ebay for about $250, but I've never taken one off or put one on.

3.  Should I just junk it and buy another motor?  My motor ran very strong, was well maintained and is super clean.  The damage to the motor was caused by me, not a malfunction of old parts

Thanks for any help guys.

First off, you should have never tried to run it with a bent prop shaft, he should have told you it would not run long if you did.

The bent shaft most likely took out the front/rear bearings and then the gears after the bearings went, so instead of just replacing a bent shaft, which would not have been a major deal, the whole LU is most likely junk now

It's not biggy to drop the LU.  Undo the shift rod and Undo the bolts on each side and the ones in the back, take the trim tab off and make sure there are none under it. some motors like to hide one under there.  With a little wiggle and shake the LU should drop.  Oh, trim it up after undoing the shift rod so it has room to come out.

Thanks Way2slow.  You always answer my dumb motor questions.  As you can tell, I am not a mechanic.  I am good with my hands though and I want to learn.  Here's another dumb question.  What is the shift rod and how do I identify it?

First suggestion, see if you they make a Clymer manual on your motor, it will be worth it's weight in gold for small jobs like this.

The shift rod runs for the lower front part of the powerhead down the the lower unit.  Some are fairly easy to disconnect, some are a total nightmare to get to, for instance this XP150 I just rebuilt, you have to take the bottom carb off the get to the thing.  I can't help you with the details on just how to do it on your motor because I've never seen one of those up close, but if you look where the shift cable connects on side of the motor, it moves some sort of lever, that lever probably goes under the front of the motor and connects to another rod about 1/4" to 3/8" in diameter that goes down toward the LU.  The rod going down toward the LU is what's got to be disconnected, usually by taking a pin or bolt out.

If the motor runs good and all it need is a lower unit. A lower unit would be cheeper than a new "used" motor. I have 75 Suzuki and they run strong. I know I have told you before, but I have an extra lower unit. Bought it for a spare 2 years ago and didn't need it. Its from a late 80's early 90's 85hp suzuki. the 75hp & 85 Hp suzuki are the same. Pm me we maybe we can work out a deal on it.