Snapped driveshaft cause?
 

Just got this picture from our current president of VT Wakeboarding. Apparently they were getting a rider up to speed and heard a clunk and sure enough the driveshaft sheared off completely. Never seen this before. Seems like if it's just a new shaft the repair shouldn't be astronomical, but it may have ruined other parts. Specifically I am concerned that being an old boat (1990 Supra Sunsport) that the Stringers have finally rotted enough for the engine to come slightly out of alignment which caused the shaft to snap. Is that a possibility? If so, we are toast. Any ideas?



(Still have no idea how to post pictures on WW so here is a link to a twitpic)

https://twitter.com/VTwake/status/37...137409/photo/1

That snapped in a strange place. All the ones I have seen are broke down near the prop. I have no Idea what could have caused that.
My guess would be a flaw in the Orignal casting. I know The G's have had some shaft issues. And they have broke away near the prop for no apparent reason.

That your classic engine out of alignment.. The shaft actually snapped at the coupling and slid back.. When you get the new shaft.. make sure you align both axis's or it will do it again..

+1

I had a shaft snap once, talked to Insurance company and manufacturer.....sometimes it does "just happen" my boat had 800 hours on it when it snapped. wouldn't rule out it being just that.

Either a flaw in the shaft that just took 23 years to fail, assuming original shaft, or a misalignment eventually resulting in a broken shaft. Typically shafts will break right at the prop or strut, from either defects, damage from striking something, damaged/imbalanced prop vibration, etc.

Check your stringers since they are wood and may be suspect. Try tightening the engine adn transmission mount bolts into the stringers. Don't crank on them, but they should snug up and hold tight. If they are loose or spin and won't tighten up you've got rotten stringers. Also knock on the stringers along the whole length with a screwdriver, wrench, or small hammer. They should sound solid and make a sharp report, if the sound is soft/dull/muffled then you've likely got rot going on in those areas.

If the lag bolts tighten up fine then just replace the shaft and align it. How long has he had the boat and how long since last engine alignment?

If they don't tighten up, plan on doing a stringer job this winter. Check supraboats.com/bbs for plenty of info on stringer replacement and restoration of these boats.

^^ agree...... Most guys with older boats with wooden stringers put a 2 inch by 4 inch steel 90 degree angle iron about 4 feet in length.. place it on top of the stinger then mount the engine and trans mount to it.... It's buys time till the big job..