750 ZXI Exahust stud breakage

[VINCE_g]

Hi everybody,

Exhaust studs sheared off - 4 out of the 6. Pulled manifold off, put in new studs, loctited and tightened up. Rode about 8 hrs, same thing - studs broke flush w/the mainfold (where the nut contacts the manifold) or where the stud meets the cylinder. 3rd time I put bolts in instead of studs (w/red Loctite), ok for 8hrs then broke again. I pulled pump - slightly bent prop and a couple of broken stator veins. Could this cause my problems? I wouldn't think so b/c it seems almost all boats have slightly dinged prop w/usually no problems. What else should I look for? Over-torquing (which I do sometimes) Manifold BTW is pretty straight - I laid it on a boring bar. Engine runs good, good compression, and doesn't seem to vibrate any more than usual.

Thanks
Vince

[Technical Support]

Any excessive vibration like an out of balance crank, driveshaft, prop, broken motor mount, etc. - is enough to break things. No, most skis do not have dinged up impellers bad enough to vibrate and break things.