yoke seal replacement

[tystick]

1990 Merc 4.3 L w/ alpha 1
while reassembling bearings, drive gear and seal, how is the alignment done with respect to each other?
before torquing locknut, bearings have to be aligned with hose clamp -

Question: how critical is the alignment as it spins at serious rpm?

 

[MJ76]

Re: yoke seal replacement

After you assemble the cluster, place a big hose clamp so it sits halfway on the inner bearing cup and halfway on the seal carrier. This will hold everything in place as you torque the pinion nut. You don't have to worry about it being perfect - everything will center itself once it's inside the case. Do check the gear shimming, though, especially if you have replaced the bearings.

 

[tystick]

Re: yoke seal replacement

After you assemble the cluster, place a big hose clamp so it sits halfway on the inner bearing cup and halfway on the seal carrier. This will hold everything in place as you torque the pinion nut. You don't have to worry about it being perfect - everything will center itself once it's inside the case. Do check the gear shimming, though, especially if you have replaced the bearings.

That is a relief but everything will center itself? When it is torqued down , how does this occur?

 

[tommays]

Re: yoke seal replacement

Its a littel more complex

As on page 3A-19 of manual 6
http://www.boatfix.com/merc/Servmanl/6/6A3R3.PDF

You need an in-pound dial torque wrench to set the rolling torque back to 6 to 10 in-pd

Unless you have the older style with the spacer that just gets torqued i have no idea when they changed over BUT i think the newer units do not use the spacer ?


Tommays

 

[MJ76]

Re: yoke seal replacement

The newer gearsets don't use the center spacer. In which case you do need to set the rolling torque with an in-lb wrench. The older style (bearings slip right onto the gear) is easier to set up - in that case the nut just gets torqued to 85 (i think) ft-lbs. The gearsets are interchangeable - if you bought new gears, chances are they are the new style.

I think the part that you are concerned with is the seal carrier, which moves around with respect to the outer edge of the bearing cups, correct?? The seal carrier has the same outer diameter as the bearing cups - the assembly won't go into the case if it isn't centered. My point was, don't sweat it too much. If you go to put it together and it hangs up going into the case, you can still tap the seal carrier around side to side with a plastic hammer to align it until you get it to go in. Once it goes in, it's centered.

The hose clamp deal works pretty well, though...

 

[tystick]

Re: yoke seal replacement

I was concerned that a micro mis-alignment would create vibration or other issues ie: premature wear etc.
At assembly, it seemed that the tolerances were not absolute and even a slight mis-alignment at high rpm would be a problem.
Evidently, bearings etc. will adjust to DB center.

 

[MJ76]

Re: yoke seal replacement

DB center, indeed. I've put hundreds of those drives together over the years and the only thing you really need to be careful with is the gear shimming. Other than that, if the seals and seal surfaces are in good shape, you won't have a problem.

 

[tystick]

Re: yoke seal replacement

DB center, indeed. I've put hundreds of those drives together over the years and the only thing you really need to be careful with is the gear shimming. Other than that, if the seals and seal surfaces are in good shape, you won't have a problem.

this is my first - with the help from you guys - I actually enjoyed it

why is the gear shimming so critical? I guess main gear would not be aligned properly and cause premature wear? I assume tolerances remain so existing shims are simply reused.

 

[MJ76]

Re: yoke seal replacement

The gears have to have a specific area of contact on the gear teeth (roughly centered on the tooth). If you look at your gears, you can see the pattern. All of the torque from the engine is transmitted across a couple of these teeth, from one gear to the other, at any one time. Too little gear mesh will prematurely wear out the reduced contact portion of the gear. Too much can cause undue friction, heat, and pressure. Either can result in failure of the gear. In many gear setups, the pattern is checked using a special paint that you put on the gears that will show the pattern after rolling the gears. Mercury uses a set of tools that allow you to set each gear at the proper location in the case. If all you replaced were the seals, and you didn't lose any of the existing shims, nothing should have changed.