Hit a stick-up/ Boat now vibrates while accelerating

[TimTJR]

Torque for prop

Phone glitched while writing so I submitted my post on a new thread.

 

[alldodge]

Being an aluminum prop my guess is one or more of the blades are bent, prop hub damage, drive or coupler.

Remove the prop and get a hand square. Sit the square up close to the edge of the prop shaft. Now turn the shaft and see if it wobbles any

If its not bent, put muffs on and run the boat without the prop and see if there is any vibration. If there is then need to look at the drive and/or engine coupler

 

[TimTJR]

I have a 2009 Crownline 18' boat with Mercruiser Alpha One and 3 blade aluminum prop. I was out on the lake last weekend and hit a stick-up that was about 2' below the surface. Afterwards I noticed my entire boat was vibrating pretty bad while accelerating. So I put the boat on the trailer to check it out. None of the blades appeared to be bent or damaged aside for a scuff mark on the one blade that hit. I gave the prop a few turns to see if the shaft was bent and it appeared to spin true. Could I have knocked it loose? So I put the boat in gear (with the motor off) and turned the prop and was able to turn it by hand. The prop turns but the shaft does not turn. So I think the nut is too loose. It is hard to turn the prop by hand but I wouldn't think I could do it at all if the nut was tight enough because of the pressure it puts on the prop just to push the boat. So I plan to take the prop off and inspect the seal to make sure it is not chewed up. When I decide to either buy a new one or put this one back on, does anyone know the torque setting for this? Is there anything else I should check?

 

[jbuote]

If the prop spins, but the shaft doesn't, that sounds like a spun prop hub..
(The rubber bushing between the center of the prop, and the blades)

You say it vibrates on acceleration.. Does it get up to speed or just rev and go nowhere.. Like you're on ice?

Anyway,
Not a pro here, but my bet is spun hub, but I wouldn't rule out bent shaft either....
How did you check if propshaft was true, if the blades move but shaft doesn't?
(the prop and shaft should have splines which interlock, so prop spinning, shaft not, is not because of a loose nut.)

Hope it helps!

 

[TimTJR]

It gets up to speed. It just vibrates pretty bad while accelerating.

How did i check if the propshaft was true, if the blades move but shaft doesn't? I spun it while it was in neutral. I spun it over and over looking at it from many angles. Nothing seemed to wobble or spin untrue.

When I put it in gear, I grabbed the prop with both hands and applied force to see if it will turn. It did not turn easy, but I was able to turn it a little. I don't think it should budge by hand.

 

[TimTJR]

I will take it off and see if the hub has spun. I can see that being the culprit for the vibration due to the slipping and grabbing. Does anyone know the torque setting for when I put a new prop on?

 

[GA_Boater]

Phone glitched while writing so I submitted my post on a new thread.

Since you edited this post, you could have completed the post instead of writing this.

 

[jbuote]

I will take it off and see if the hub has spun. I can see that being the culprit for the vibration due to the slipping and grabbing. Does anyone know the torque setting for when I put a new prop on?

You can make marks on the inner and outer hub and run it.
If the marks don't line up anymore, the hub is spun.
You should be able to turn it one way by hand, but not the other when in gear.
Since you said you can (with some force), that still makes me think spun hub, but the gurus may have better ideas...

I think the torque is 55ft lbs on Alpha and Bravo One..., then just a little more till the locking tabs line up..

(EDIT: I see the other thread has been merged here.. Missed that thread...
I'd listen to AllDodge first.... )