I learned first hand what a "little" play in a shaft will do. Test running my 13hp modified mad mud motor plan longtail yesterday, I had a vibration that went from bad to worse very quickly. Motor was turning about 4,000 rpm when the cavitation plate began to wobble with the vibration and a quick snap of the throttle by my friend who has been helping me build along the way and the hill 8x4 prop struck the plate about 6 times. Prop seems fine, but the cavitation plate was a little jacked and the prop shaft bent to a 45 degree angle. Needless to say, I am no pro, not even an amateur, definitely still a rookie with tons of learning left to do. But please, anyone who may read this, if there is any play in your shaft or anything on your motor please address the issue immediately. Though no one was hurt with my accident, someone very well could have and I am lucky all I am out is some 1/8" plate and some 3/4" cold rolled solid round.

Can you post pictures of the end result?

I'm curious as to what went wrong that you bent the end of the shaft 45 degrees?

(I broke my handle off my motor running full throttle in a turn, don't feel too bad.....thank goodness I was wearing my kill switch)

Ill get some pics of it tore apart. Ive already started to pull it apart to rebuild it. Itll be a few days. for now the motor lives at my friends where the welder and welding skill lives lol

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I'm interested as well. Are you running a bushing or bearing on the prop end? Couple of weeks ago I ran over one of my set lines and pulled a 4' piece of rebar into my GD. By the time I realized what happened it had bent the rebar in a circle and threw it out. Only thing I could find was a little ding in the prop so we cut the line out of it and carried on. Couldn't believe the rebar didn't even bend the cav plate!

Ive got a bushing down there. Another issue was my prop was about 3.5 inches off the end of the dom tubing. So the vibration was even further out.

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I could see where you would have problems with that much gap between the bushing and prop. These props are heavy.