Anyone ever break a v drive shaft?

[Timmy!]

Long story short, my buddy has now broken 2 v-drive shafts on his Epic and we are just curious if anyone else has ever broken even 1 without hitting something major.

Last year he was driving and the boat just stopped and couldn't figure out why so he had someone tow him in only to find out that the shaft and prop were completely missing! Turns out the shaft was broken off inside the trans. Fast forward to yesterday, boat doesn't move when put in gear and he hears water coming in. Dives under the boat to find the prop resting against the rudders (boat has twin rudders). Pulls it in and the prop is undamaged and the shaft is broken off at the notch that goes into the transmission but this time he has it and the prop to examine. It looks like the end of the shaft has been heated or something. I can't imagine the force that it would take to snap that thing like that, it's solid steel! He's calling the insurance, repair shops, etc today to find out wth is going on and why it looks like it was heated.

[brett22i]

Very possible to snap under power. I have seen very large drive shafts shear off on yachts under load. Resulted from a flaw in the production of the actual shaft, not builders fault. If were him I would make sure not to use the same shaft manufacturer for the replacement. I would also make sure everything is aligned properly, but would think it would damage the transmission internals before shearing a shaft?

[Timmy!]

That's what we were thinking, maybe a flaw in the shafts themselves and not the person who put it in's fault.

[NICKYPOO]

I don't know, bad batch of prop shafts? There would be others if this were the case. Is it possible a misalignment of the twin rudder system is causing some sort of odd cavitation reverb off the back of the prop causing an oscillation that in turn (no pun intended) ultimately causes shaft failure? That one's pretty thin too. Maybe the shaft strut misaligned or even the V-drive unit misaligned? This would cause an uneven load to the drive side of the shaft causing excessive heat and ultimately failure. Two prop shafts failing in the exact same way? Too fishy for me to be just a simple parts failure.

[Oklahoma Breakdown]

I don't know, bad batch of prop shafts? There would be others if this were the case. Is it possible a misalignment of the twin rudder system is causing some sort of odd cavitation reverb off the back of the prop causing an oscillation that in turn (no pun intended) ultimately causes shaft failure? That one's pretty thin too. Maybe the shaft strut misaligned or even the V-drive unit misaligned? This would cause an uneven load to the drive side of the shaft causing excessive heat and ultimately failure. Two prop shafts failing in the exact same way? Too fishy for me to be just a simple parts failure.

x2...especially since it is shearing off right at the entrance to the tranny. Sounds like something is misaligned. Hope the insurance covers it.

[Tantrum1]

Where exactly is it breaking? I broke one last year on my 2004 20V. It broke about a 1/2" from the threads where it goes into the v drive coupling. But mine was do to a bad shaft. You could tell because it corroded from the inside out. Take a look at where its broken. Is all the broken end shiney or is it partially black with a small amount of shiney. That will give you an indication of a bad shaft or of misalignment issues. I took my broken shaft, my coupler, and my prop to a machine shop and the made me a new shaft out of high grade stainless for cheaper than buying a new one. Or get your buddy to buy a Tige... just teasing.

However all the advice above is strickly just my opinion.

[Timmy!]

Turns out that the guy who installed it didn't know what he was doing and was heating the shaft to put it into the coupler instead of pressing it in. The heat weakened the shafts (Same guy put both of them in) and they eventually broke.