Separate the Upper from the Lower
Watch the video:
- Disassemble Drive Shaft Housing
Measure Prop Shaft Run Out
It is possible that the shaft could be twisted or bent in such a way that it still runs true here. A more accurate way to measure the trueness of the shaft would be to mount the shaft between two live centers on an inspection table. But, this method will suffice.
Measure Prop Shaft Deflection
Grab the end of the shaft and move it up and down toward the dial indicator. This measures play between the prop shaft bearing and the outer race or bearing cup that is pressed into the bearing carrier.
Measure Overall Pre-Load
Drive Shaft + Prop Shaft
Even if you are only replacing the seals, or drive shaft for that matter, you must make this measurement. Write it down. This is how you will determine how tight to make the bearing carrier retaining ring when you reinstall the bearing carrier.
This measurement can also be taken by putting the prop nut on and using the inch pound torque wrench and a socket on the prop nut. I find the method in the video more convenient. Do not use the socket on the drive shaft (that's the vertical shaft) to torque on the shaft while loosing or tightening the Pinion Nut. The socket will jam on the splines and mess them up. Holding the drive shaft for that purpose requires buying another tool.
Remove the Bearing Carrier and the Prop Shaft
Watch the videos
- Remove Bearing Carrier
- Remove Propeller Shaft
Measure Pre-Load of Drive Shaft
Take this measurement and write it down, even if your only replacing the seals.
Measure the Pinion Height
If you are not removing the drive shaft, you don't have to measure this. There is no tolerance specified for this measurement. It is to be .025 inch + or - nothing. There is no reason to think that once new bearings are worn in, that this would stay exactly .025 inch.
That Pinion Height Measurement tool is expensive. But, at least now you know what it looks like.
Measure Backlash
If just "doing seals", you don't have to measure this either. Once the drive shaft is shimmed up perfectly, backlash is set by adding / removing shims from behind the driven gear.
For me, taking all of these measurements, along with visual inspection of the gears etc., gives me an idea of the over all condition of the lower unit. If the bearings are worn in, (not worn out), the measurements should all still be within tolerance. If some measurement is not within tolerance, I see no point in "re-shimming" the drive shaft or driven gear without replacing the bearings at that location. If the unit is full of metal flakes and debris, buy some more tools and take the whole thing apart.
