I blew a lower right in mine at 75, pulled back on the throttles as the engine wung past 6k. Not much fun.

I take it then that the failure is RPM related?

With mine when the gears let go it allowed the motor to over rev, so not because of rpms i dont think.

I've had drives let go.... unfortunately pretty familiar with that!

I guess with the TRS... trim and angle and load/rpm are the issue? TRS drives are new to me... trying to understand their weak points (if any).

Uppers are pretty much bullet proof. The lower lefts seem to be too. Only problem ive had is one lower right let go. They seem to be the weak point. The driven gear is behind the pinion instead of in front of it like the left and less supported.

The carrier bearing on mine was corroded, so i bought a corrosion free right hand drive and blew it in 17 hours, put the corroded one back on for now with no issue. Maybe that drive had a prior issue.

I had a 89 311 with TRS drives and 420hp motors. I don't know what it was about that boat but it sat a lot higher in the water then the one that my buddy had that was the exact same set up. I have since sold that boat.

TRS drives like to be deep in the water. They DO NOT like to have the prop surfaced. When you trim it way up the prop starts to capitate and they blow the gears. This is what I did being stupid. It did hit 74 GPS however LOL I think if you get between 68 and 70 then I would be REAL happy.

They are great drives. Love the way that they shift. They are well with in the rated power. The only thing I would say is don't mash the throttles out of the hole and don't way over trim them and you should be good. They are for the most part very strong drives for your set up.

Update!

Test data...

27P solid hub Mirage props. Not in perfect condition.

Max speed of 67-68 GPS at 4600-4700. I ran out of room where I was testing, and the 'Bay was too rough to play in this afternoon (managed to run 54-55 MPH in five footers when I was out there... big storm coming in).

I am loving the cruise speed... in the 50's at 3300.

Thinking of having the props cleaned up, and removing an inch of pitch... 26P Mirages. That would put me at 4800-4900. Current slip numbers at are 15%.

Should I go this route?

On thinking about it... was probably three to four footers with some deep holes here and there. I got about two miles out and thought it would be best to come back in... the ride back was a soaker!!