Rubex RBX-105 Hub issues

[gumbyaz]

I have had my boat for just over a year. I had no problems getting the Rubex prop and hub off of my Volvo SX-A last year (it was brand new from the shop I bought the boat at), but then when reinstalling it last year after initial maintenance noted that it seemed to take a lot of wrenching to get up to the reco'd torque value. This year when I went to pull it off I found out why: I had to use a puller to get the prop off, and then the hub was stuck on the shaft, so had to use another puller to get the hub off. Turns out, the interior hub splines were "mashed" about 1/8" where they rode up the shaft onto the straight part of the shaft forwards of the shaft splines.

Thinking maybe I had a defective one sold to me with the boat, I ordered a new RBX-105 hub kit. It got here last night and I tried test fitting the thrust washer and hub. There is almost a 1/8" gap between them!!! If I assemble the prop and torque it down again like last year, it will just trash the hub splines again. This can't be how it is supposed to work. Pictures are attached of the gap with the new hub/washer, and of the damage to the old one.

I tried sending Solas/Rubex an email last night. No response yet. Anyone else have problems with this hub on a Volvo drive?

I did find an old thread that seems eerily similar, but no good fix/conclusion to it:

https://forums.iboats.com/forum/gen...-sx-drive-prop-replacement-issues-pics-inside

 

[89retta]

Is the thrust washer the one that came with the kit or is it a factory Volvo part ?

 

[gumbyaz]

It is the Rubex one that came with the new kit. Both the old and new thrust washers are identical.

 

[Watermann]

Are the hub spline teeth damaged from being forced onto the bevel of the prop shaft? The other end of the hub that's undamaged is beveled so I would imagine that is the end that goes on first.

 

[gumbyaz]

Are the hub spline teeth damaged from being forced onto the bevel of the prop shaft?

Yes - the interior hub splines are forced over the beveled end of the shaft splines towards the front of the boat, right at the point where the shaft splines end and the shaft becomes smooth/round. Since the hub is softer aluminum, it gives way before the harder stainless shaft.

The other end of the hub that's undamaged is beveled so I would imagine that is the end that goes on first.

Scratching my head on this one - if the spline end of the hub is placed on the shaft first, the hub will be hanging about 3 inches out past the end of the shaft. I am pretty sure I have it going on the right way.

 

[Watermann]

Yeah the pics are making m scratch my head, I'm trying to figure out that splined piece, it looks like it was removed from the hub piece that goes in the prop shell. All my props are hub systems too Mercury black diamond and Turning Point but they don't look like yours.

 

[gumbyaz]

Still not sure what is wrong (shaft made wrong or hub made wrong). But I was able to rig a fix to get back on the water and not waste any more money. The round part of the shaft is about 15/16" diameter right after the splines end. I used a 1" hole saw I had laying around (15/16 hole saws are hard to find) and carefully put it in the hub from the boat side of the hub so as to not scratch the smooth part of the hub bore. The hole saw centered very well once it hit the splines, and I took out about 1/8" of spline, sneaking up on it in small bites until it all fit on the shaft and there was no gap between the hub and thrust washer.

Cleaned it up real well to remove the shredded aluminum. Re-assembled. The torque setting felt normal now. And best part - trial disassembly after one day on the water: slid right apart like it was made of warm butter.

I can't imagine 1/8" less spline will cause catastrophic failure, at least not with only a 4.3 motor.