TOPIC: Drive shaft info Mark78

Figured I'd start a new one on this subject. The drive shaft has some up and down play. When I pull it up and spin the shaft no noise. When down, gear noise occurs. I'm convinced I need to tear it down and my question is, do I have to have special tool to get drive shaft seal out or can I knock the edges inward where I can grab hold of or what?? Thx, Joe

That noise is normal. When running, the centripetal forces of the gears push them away from each other, driving the driveshaft upwards. Unless there is excessive bearing play, or you are hearing bearing noise or feeling a catch in the bearings, I wouldn't bother pulling it down.

I have water in my oil and we went through a big discussion yesterday and there was clanging from what I believe was the lower unit, especially when it wound down. A couple of the experts said tear it down and see what I have.Thx,Joe

9 out of 10 times its your driveshaft itself causing the problems. It wears/rusts in the area where the seal contacts it and causes it to leak directly under the water pump. Can be fixed by welding up the driveshaft or a spedisleeve.

If you want to do it right. Pull the Prop Shaft out. Then take the nut holing the pinion on off. Then the driveshaft can be pulled up and out. Usually the driveshaft is hard to pull. Put the driveshaft in a vice and take a 2x6 about 3 foot long and beat the case away from the drivesahft. It will pull out.

Then you can inspect your true problems. Keep track of your shims. there will be brass shims behind most every surface, so pay attention and catalog them.

I doubt you have any real problems as far as broken teeth or anything like that.

So either button it back up and deal with changing out your lower unit oil very often. Or get to getten and tear it completely down.

Also get the merc manual. It has pics, and much much reading that will help you more than we can. You will love it.



conrad

Joe,
If you discover that your lower unit is a mess inside - I have two real nice short shaft lower units for that Merc.
Write direct to me at frankenmerc at comcast dot net if you become interested in that solution.
Thom

The water pump cartridge has to come out, along with the upper seal carrier before you can get the driveshaft out........not a fun job if there is too much corrosion! How much "up and down" play in the driveshaft is there?? There really shouldnt be much at all, given the gear lash adjustment is .005". Joe.....you definately need a teardown!!


Jim S.

Thx Jim, Thom and Conrad. Ya'll are at the top of my learning list. I've been sanding on my Invader so I haven;t checked this lately. I'm not sure what I'm going to do yet, but want to do something quick. That's the boat I use and it's hot down here!! Thx, Joe

joenawlins wrote:

Thx Jim, Thom and Conrad. Ya'll are at the top of my learning list. I've been sanding on my Invader so I haven;t checked this lately. I'm not sure what I'm going to do yet, but want to do something quick. That's the boat I use and it's hot down here!! Thx, Joe

You're quite welcome Joe!
Well, if you have excessive up and down movement in the driveshaft, my guess is the bearing frose ( as is evident in the water in the oil ) and spun in the housing. If that's the case, the housing is toast and you better contact the Doc! That's the quickest, easiest route to take.....

JS

I did, Thx..

Ill be honest I have never FULLY taken my dockbuster lower unit's apart. Im assuming they are like my MK 55 and the water pump housing comes out when you pull the drive shaft. All in one swoop.

I just tore another MK 55 down today and thats how I did it. If there is a bunch of up and down movement then that top bearing musta let go. I wish you luck.

At least they are simpler in there. No extra gears and stuff like that. No lining up shift shafts etc...
conrad

What purpose do the water valves serve and if I get the spedisleeve will it just go on the drive shaft without pulling it??

the valves direct the water in forward and reverse.1 for foward 1 for reverse.