vibration

I have a 1997 5.0 litre Mercruiser Alpha One I/O. I was traveling at a low speed with a 4 blade stainless steel prop and hit a concealed rock. The collision caused one blade to become quite severly bent. I have had the prop repaired and I put it back onto the shaft. It now seems that I may have a fairly slight vibration.

Our lake levels are high, and we are not able to produce wake on the lakes at this time, so I have not been able to open it up, but at low speed, it appears that there may be some vibration. It also seems like in reverse, I am not getting the power that I should be getting. I have looked at the propeller shaft, and it does not appear bent, but I have heard that with the stainless steel prop, hitting a hard object may not only bend the prop, but also the shaft.

I am a complete neophyte when it comes to boats, and I am a first tiime owner. Does anyone have any suggestions. When I put the prop back on, I put it on using the yellow plastic prop wrench. I got the prop as tight as I could get it, but one really isn't able to get a lot of torque on those wrenches as they bend when you get it tight. Could this be part of the problem?

Re: vibration

You may have bent the prop shaft. You will need to have it checked for "run out" with a dial indicator. It seems to me .002 to .003 thousands run out is acceptable.

Re: vibration

Did the prop look like new after the repair? If the prop is a little bent or unbalanced you will have a shimmy.

Re: vibration

I bought a used prop once that was "supposedly" repaired by a propeller shop. That prop had blades that had completely different pitches from the other blades. The prop was also out of balance. What type of propeller repair place did you take this to?

This is where my props go:
http://www.wilmingtonprop.com/aboutus.shtml

They are an outstanding propeller repair facility.

Re: vibration

The prop repair looked like it was done well. I also have a 3 blade stainless that I put on while the 4 blade was being repaired; it also appeared to have a little vibration.

I took it out this evening, and the engine/outdrive also seemed to be making a slight strange "noise", like something just wasn't right. Would a bent propeller shaft also cause noise?

I don't know if my mind is running with ideas due to paranoa, or if there is really something wrong.

The boat was running great, and was taken care of very well before my purchase. Do you think that there would be anything else other than a bent prop shaft? It all seems to coincide with the rock strike. Would that cause anything else other than a bent prop shaft?

I really appreciate all of your thoughtful assistance.

Re: vibration

Double post

Re: vibration

Have you taken off the prop and run it in gear without it on to see if you detect any visible wobble in the shaft? You should really do a runnout test on it but if it is grossly out of whack you would see it right away.

Or just take off the prop and turn it by hand.

One more thing...you can't tell by eye if the pitch is out. Give Wilmingtom Propeller a call and just tell them what you are experiencing. They are pretty friendly and might give you some hints on what to look for or to try.

Re: vibration

Thanks Bruce. I appreciate your help. I have had the prop off and turned it by hand, but I did not see anything noticeable. At the risk of sounding like a complete idiot, what is a "runnout test"?

I am strongly considering taking it in and having someone give it the once over, but my skeptical side always has me concerned about taking something in without any real knowledge about potential problems.

Can you think of anything else that the rock strike would have caused? Would it likely cause damage to anything other than the prop shaft and/or propeller?

Re: vibration

Here is a guy checking run out:

http://www.youtube.com/watch?v=nzSjIV9tr3E

Re: vibration

Looks like a job for someone with more knowledge and equipment than me. I presume that a marina will be able to take care of that for me. Hopefully, if the shaft is bent, they can repair as opposed to replace.

Seems to me like it has to be something with the shaft. Thanks again.

Re: vibration

KDLHARLOW said:

The prop repair looked like it was done well. I also have a 3 blade stainless that I put on while the 4 blade was being repaired; it also appeared to have a little vibration.

I took it out this evening, and the engine/outdrive also seemed to be making a slight strange "noise", like something just wasn't right. Would a bent propeller shaft also cause noise?

I don't know if my mind is running with ideas due to paranoa, or if there is really something wrong.

The boat was running great, and was taken care of very well before my purchase. Do you think that there would be anything else other than a bent prop shaft? It all seems to coincide with the rock strike. Would that cause anything else other than a bent prop shaft?

I really appreciate all of your thoughtful assistance.

Click to expand...

Have seen alot of gear damage from SS props hiting rocks!!!

Check the gear lube for metal partical, the lower drain plug should have magnet in it, if it is covered with metal peices CALL YOUR INS. CO.


RJ

Re: vibration

Limited-Time said:

You may have bent the prop shaft. You will need to have it checked for "run out" with a dial indicator. It seems to me .002 to .003 thousands run out is acceptable.

Click to expand...

Marina just informed me that the prop shaft was bent very slightly .004; he informed me that this was within merc specs, and that replacement was not necessary. He further indicated that they pulled the outdrive and that the gimbal bearing and u-joints looked good, they drained some of the gear lube and there were no metal particles in there.

Basically he indicated that the vibration may be coming from the slight bend and that the prop may not have been repaired properly. I am going to get it out and see what the performance is; if it is still vibrating, I guess that I will have to have someone look at the prop to determine if it was repaired properly.

Thank you to all who responded to my question. If you have any other suggestions, please let me know.