Vibration in lower unit

[mike]

I have a 22 ft Pursuit with a 230Hp Mercruser outdrive.
I hit a sandbar off Boles Harbor channel this evening.
The boat was going about 6 mph.I immediately shut down the engine and raised the lower unit.
After freeing myself from the sandbar I noticed a vibration at about 1500 rpm.
I put the boat on the trailer, drove home and put the water jacket on the motor and started it up and put it into gear. Ran the engine in gear up to 3400 rpm and no vibration. I know the unit was not operating under any load. The prop had no physical damage except the paint was stripped off.
I hope I just bent the prop ???? any other diagnosis out there ????

Thank You

[REW]

If you can check out the boat in the driveway - and run it up - and find no vibration - it is likely that it is only a bent prop.

A good check is as follows:
Remove the propellor
Start the engine (with cooling water in place of course).
As you rev up the motor - check the rotation of the prop shaft and insure that it is running true. You are checking to see if the prop shaft is bent. You should be able to put your finger on the end of the prop shaft when the engine is running at a good rate of speed, and there should be no movement.

The next time you go out - try a known good prop and see if the vibration is gone.

Then take your prop in for truing and balancing.

Take care

REW

p.s.
If you find any movement when you do the test on the engine - the outdrive is going to have to be pulled apart and the prop drive replaced or straightned. If you find the prop shaft bent - a good prop shaft can often straighten it with a good press and a dial caliper.

[seahorse]

I don't think anyone would recommend touching the propshaft while the motor is turning it. An easier test for a bent shaft is to put a phillips screwdriver in the centering hole of the shaft and spin the prop by hand. Any movement felt in the screwdriver signals an out of true condition.

[REW]

Right on -
I was using a figure of speech.
Your method is much safer and my actual intent.
Thanks for your correction.

REW