Broken driveshaft

[jantto]

I just broke my driveshaft and pulled it out on the beach. Midshatft bearings are excellent and splines looked good. Any ideas what ould cause this? Bad midshaft aligment or motor aligment, or just junky shaft. It has like 10 hours on it, so almost new. I have no idea what brand it is. Motor is TPE +5mm, rickter xfs hull. I will replace it with OEM shaft I have ,but do not want broke that one too. Broken shafts I have seen have snapped right next to impeller..

 

[Sasquachcrap]

Ewww

 

[jantto]

 

[Pro-pulsion]

Can you get a better more close up pic? If it looks like there are chips out of it then I would say it was improperly tempered making it brittle. That's a tough area to break a shaft since the worst of the load will actually be in the middle to resist flexing under torque. If anything, it should have twisted somewhere in the middle well before breaking in the center of the spline.

 

[jantto]

Thanks for info! Sound like you know what you are talking about. I will get better pic tomorrow. Shaft is in my friends trunk right now

 

[ajmps1]

Poor spline engagement. And you suck, WA WA WA my motors too powerful WA WA WA

 

[Proformance1]

Id go with too less engagement also. Oem shaft on oem 155 equals a bad day

 

[snowxr]

X3 I'd say that your shaft was too short (my condolences to your wife or gf) and you were transmitting the load through the tip with it only inserted a short distance into the midshaft.

 

[jantto]

HA ha!
Ok, thanks for advice! I will check engagement and get longer shaft if it is too short. Here are the pics anyway..

 

[Sasquachcrap]

Was it a set back pump?

 

[jantto]

Poor spline engagement. And you suck, WA WA WA my motors too powerful WA WA WA

Well, but my motor hits like mofo..

 

[jantto]

No, it is 155 oem

 

[jantto]

I know I should get skat pump.

 

[mike b]

Get a hardened driveshaft from H2O. That's what I am running after breaking my OEM shortened shaft.

 

[xXx Octane xXx]

Is there grease on the fracture surface in the area directly above your pinky finger in your picture?

Most of that fracture surface shows torsional overload but the dark area on the fracture surface makes me suspicious that it may have been cracked for some period of time prior to the failure.

OEM driveshafts are through hardened 17-4 PH with a hardness of 42-43HRC.

I would argue with anyone claiming that non-modified OEM driveshaft is inferior to any aftermarket driveshaft on the market.

 

[Fro Diesel]

Can you get a better more close up pic? If it looks like there are chips out of it then I would say it was improperly tempered making it brittle. That's a tough area to break a shaft since the worst of the load will actually be in the middle to resist flexing under torque. If anything, it should have twisted somewhere in the middle well before breaking in the center of the spline.

Or twisted near the prop, if something jammed in there.

 

[Pro-pulsion]

I agree with Octane, there are a few lines in the first pic that cross the diameter of the shaft starting at about the middle and up toward your thumb. It appears that those are fractures.

 

[jantto]

So I took motor up and measured spline emgagemen -25mm. That should not be an issue or what? I will throw my oem shaft in and see what happens...

 

[augustaf]

My Superjets with stock 144 pumps have about 35mm spline engagement, the op's 25mm would appear to be a bit short. Shaft splines appear to be about 42 mm long. Of course you need a bit of travel space, should you land your ski into a sand bank, tail first. If shaft splines run out of travel they will lock to the midshaft. Don't ask how I know.

 

[Tyler Zane]

I press the midshaft as far in the midshaft housing as it will go and then add washers behind the midshaft coupler to made up the difference. It will get you about 7mm more engagement.