Broken prop shaft on Verado 300 , 101 hours only

[Range]

I am new in the boating world and I would like to know if this has ever happened to anyone of you. I read in a forum that this is because of barking the props but from what I know and see on Youtube, rib boats are very fast, light and comfortable. Even if you are riding fast you still feel comfortable and confident riding it. But before I broke the propeller shaft, I played around with the boat at around 65 miles per hour on 2-3 feet chops of water for about 7 mins with 6 other passengers and I could feel that we were flying. The props were in and out of the water. The next day I drove around at cruising speed of 35-40 miles per hour. After a few hours, I refueled. Afterwards, I was cruising at 40-45 miles per hour when suddenly the RPM on the starboard side went up. Upon checking, we discovered that I do not have a propeller and a propeller shaft anymore.

Any thoughts on this? When we rode at 65 mph the day before, my trim was up. Do you think I stressed the propeller shaft too much?

My boat is a 10 meter rib twin Verado 300 and lower unit is 4.8 in diameter. Bravo 1 props with Flow torque 2

[two stroke mick]

Was the shaft that broke on a counter rotataion engine?

[Range]

Pics of broken shaft

[Range]

Yes it's a counter rotation

[boristhebold]

When you were 'flying' out of the water did you hear any alarms going off from the engines over revving ? Sounds to me like yes you have stressed the mechanicals to breaking point. Your engines I would have thought should have been giving you a lot of warning, if your revs go too high it should cut the engine.

[two stroke mick]

I recall on this forum that a rib user with similar sized engines had a similar problem on at least two occasions on the CR engine. I just cannot find it now.

[A1an]

You are new to boats?

[Range]

Broken prop shaft

[Range]

Yes 6months

[two stroke mick]

see this it might be of interest but I know that there is more I think if you send a message to 250kts the original poster he may be in a posityion to advise


http://www.rib.net/forum/f36/counter...es-49758.htmlr

[Range]

Originally Posted by boristhebold

When you were 'flying' out of the water did you hear any alarms going off from the engines over revving ? Sounds to me like yes you have stressed the mechanicals to breaking point. Your engines I would have thought should have been giving you a lot of warning, if your revs go too high it should cut the engine.

I did not hear any warning alarms at all

[Range]

Thanks two stoke mike

[Bigtalljv]

Are you backing off the props when coming out of the water or just leaving it pegged while you fly? I would never profess to being a racing boat driver but I have seen it on TV. I would think the out of water to in water transition would create a huge stress on the engines as the prop goes from biting air to biting water. Water is pretty hard and immovable on an impact like that.

I know there are some racing drivers on here, I am sure they will be along with suggestions.

jason

[Range]

I left it peg for 7 mins maybe

[Will75]

I did about 30 hours on a twin Verado 300 RIB at close to 55 knots most of the time and the engines where fine even in pretty choppy conditions. It is true that active throttle control is important at those speeds and when the vessel is leaving the water but I am sure Verados have seen worse treatment than you have described. So in conclusion I think there must have be an underlying defect to cause this but nonetheless a more sensitive approach to what are a phenomenal engine package is a good idea.

[Steve_B]

We have run 250 Verado's now for 5 years, they are cracking engines.

We had the "standard" gearbox's on them for the first 3 years and found that every 360days (I kid you not), the counter-rotating gearbox ate itself. This was, in year one replaced under warrantee, and in year 2 as a goodwill gesture.
In year 3, when it failed again (remember the other gearbox was still original and in first class condition) our service agent had discussions with Barrus. In a fabulous act of customer service, Barrus replaced both gearbox's for the larger heavy duty box's.
Since then, they have both operated flawlessly. I would say the box's are smother and quieter. We had to tweek the prop's to get the rpm right at WOT.
I understand that since 2011/12, Barrus no longer supply the counter-rotating engine with anything less than the heavy duty gearbox.
My advice would be to approach the supplier of the engine and if that fails, talk to Barrus.
Regards
Steve

[Oscarguitar]

Barking the props is like lifting the drive wheels of your car at 70mph and dropping them back down again. Something is gonna break. Looks like a 600hp 10m rib is just too much for a first boat. Perhaps get some training and learn to to walk first....

[Steve_B]

Having taken the time to look at your pictures, it is the output shaft that has sheared.
We never had that problem, it was the internal gears that broke.

I am also concerned by the picture in the 3rd post. The bottom of the skeg looks wrong.
It has a flat bottom which looks unpainted? Has part of this sheared off? All our gearbox's have had a nice smooth profiled finish.
If not, it looks as though you may have hit an under water object, hard! This would have certainly been enough to shear the shaft too.

[Searider]

To determine what might have caused the shaft to fail would need the fracture surface to be inspected by a specialist.
This would indicate if the failure was sudden, due to a shock load or gradual due to fatigue. There may even be a manufacturing defect that can be seen.
I can suggest Materials Technology in Totton.

See what your insurers say - and suggest a specialist inspection.

[Range]

Mercury warranties the broken prop shaft and propeller on my starboard side , I'm asking them to change my port side also , cause I lost my confidence on it already .