What would cause the Yoke to break at the splines where it goes into the upper gear on a Bravo One Drive? The drives have @ 250 hours on them and I just completed updating the engines to @ 500 hp and added Stellings Extension Boxes (set up at the highest holes). I have never had any drive issues before and after 15 minutes of testing the new set up, the yoke let go. I see some posts expressing concerns with using the Stellings boxes due to the solid connection between the engine and drive (no rubber drive coupler) but could this cause a failure in 15 minutes? Any input would be appreciated as I would like to understand the cause before putting it back together.

Thanks.

They rarely break there unless over powered. Friend has the same boat as you and I.. his is 750hp with Stellings box.. Mine has Imco box. No issues with the small yoke. I doubt is it an alignment issue, but maybe others have experienced the same failure. Only ones I have seen with small yoke broken at the splines were blower motors..
What prop are you running??
Sorry not much help on this one.
Dick

Thanks for the input. During the testing I was using labbed 29" Mirage Plus props. I was going to try some 30" Bravo One props next but never had the chance.

Another question on repairing the drive. The drive gear is galled on the inside surface from the spinning broken yoke. Is this surface important to supporting the yoke or can the gear be reused?
Thanks.

This same thing just happened to me!

500HP - snapped it right off. I think it is the bearing carrier. Needs to be shimmed because it puts excessive force on the shaft.

PM'd you - hit me back

Based on advice from Keith Atlanta who had the same yoke failure and is also running stellings boxes, today I removed the bearing carrier in the extension box for inspection. There is no obvious damage ( I currently cannot disassemble it because my snap ring pliers are too small). The drive shaft to drive yoke flange has no play in the bearings and spins free. Before removing it I slid the alignment tool in again and it was perfect. I plan to contact Stellings this week to see if they have any suggestions. Anyone have any other ideas? I wish I could blame the failure on ungodly engine torque but that is just not the case...

Thanks.

I ran mine all summer with no problems, KOW. 500 hp 489ci motor, box all the way up. Although, I do have shims under my carrier, had to to get the alignment "perfect", the tool went in, but it went in a lot easier after shimming.
I think I need a new bearing though, any body know how much $, where?