Electric shift upper driveshaft stripped

[salvageyard saviour]

Just curious,
I recently took apart a high profile 225 - 245 HP drive for parts and found the water pump shaft and the upper shaft stripped.
In a past thread Howard Sterndrive mentioned this as common but didn't explain why.

What causes this ? It looked like a pretty dramatic failure. The splines looked clean and good right up to the failure where they were almost completely smoothed down.
I've seen coupler splines that get "cupped" before they fail but this didn't look like they went through that.

Also both electric shifts I took apart had the water pump impeller housings broken to pieces. Is this related or part of a different issue?

The main reason to ask : Is there a certain way to grease them or maintenance to do so this won't happen ? Those puppies are expensive !

 

[Scott Danforth]

Its a poor design, and the achiles heel of the OMG drives

they all fail

Buy new shafts, rebuild your drive and go boating

 

[salvageyard saviour]

Thanks for the reply.
I don't plan on using this drive. I only got it for the upper gear set and lower unit.(drive came with a lot of other goodies also)

Just wanted to know why ? and if there was something to do to slow it down from happening to the one I plan to use.
Do you think when winterizing that I clean and regrease splines it would help ?

I'm guessing the blown up water pump housings were from trapped water freezing. The regrease idea would insure there's no water in there over the winter.

 

[kenny nunez]

As the swivel bearing wears on the lower gear case the splines start to run out of alignment. Also there is supposed to be a rubber splined seal that must be sealed in place which holds the grease in the lower pinion shaft splines. If you replace the pinion shaft the seals have to go in after the shaft is installed otherwise the seal lip will reverse and the spring will fall off. The early models just used the locknut to hold the gear in place, later models also had a tapered cone under the nut that held the gear in better alignment. The plastic shims under the front bearing cover set the ballgear shaft rolling torque around 6” lbs. There are shims under the rear bearing cup of the ballgear shaft that sets the backlash. Without the shimming tools just be careful to keep the shims in order if you are going to swap the gear set to another gear case.

 

[salvageyard saviour]

Yes ! that swivel bearing makes sense.
Guess that's why I've seen so many of those for sale. I couldn't see why they would be so important to keep in top condition.
I'll be sure not to use the swivel housing from that lower unit (or the water pump cover).

Thanks for mentioning that. Someone might just assume that if a part worked in one it would work in the other, without considering those components. I've gotten a manual that's not a " knee pad " (as someone is famous for saying) and I've made gizmos that measure bearing pre-loads, backlash and rolling torques pretty close.

 

[Scott Danforth]

to your question, you can slow down the deterioration of the splines, however you can not prevent it unless you were to ditch the IC engine, install an electric motor with a fluid dampening coupler. every cylinder pulse loads up the splines, then unloads them, so they basically get hammered to death.

the swivel bearing alignment simply speeds things up.

like I said, poor design.

a rubber damper would help a bit, however, that would require re-engineering an obsolete drive.