View Full Version : Prop shaft bent or motor misaligned?

05-16-2012, 07:22 AM
Took the following video of my propeller shaft. You can see the packing nut is moving back and fourth. Wondering if anybody knows if this is a bent shaft or if something is just out of alignment. I feel no vibrations when driving.


1995 Mastercraft Maristar 200 VRS

05-16-2012, 09:25 AM
To test for a bent shaft you can do the following. This is much easier and faster if you have a couple of helpers.

While on a trailer, remove the prop (safety first), have someone hold a garden hose spraying water on the strut bushing, crank the motor, put it in gear and give it a little gas. Place a wrench on the shaft as it is spinning. If the wrench jumps around slightly, you may have a bent shaft or it could just be a worn out strut bushing. If you can't keep the wrench on the shaft, the shaft is likely bent.

Don't leave the motor running long without water going to the raw water pump.

Good luck and let us know what you find.

05-16-2012, 10:38 AM
Disclaimer: I didnt check out the video.

If something is vibrating, then theres a good chance that something is bent. Most likely the prop or shaft.

Misalignment will generally not cause any driveability symptoms. Instead, you'll side load the strut and transmission internals, and things will wear (and fail) prematurely. If you cant spin your prop with one finger, then you likely have alignment issues.

I have seen some boats that were so severely misaligned that the shaft was riding on the brass log where it exits the boat.