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Jason, Marine Mechanic
Category: Boat
Satisfied Customers: 15669
Experience:  Degree in Marine Technology. Gas and diesel marine mechanic.
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I have a bad vibration and knocking when I put boat in

Customer Question

I have a bad vibration and knocking when I put boat in drive. Hit a stump in water after that is when it started this.
Submitted: 1 year ago.
Category: Boat
Customer: replied 1 year ago.
I can see the drive shaft vibrating where it goes through transom. p.m.
Expert:  Jason replied 1 year ago.

Hi Kevin, my name is Jason.

I read what you wrote, how is it I can help you, what kind of questions did you have?

Expert:  Jason replied 1 year ago.

Hi Kevin, it looks like you read my reply and logged off, did you still need help with your issue?

Customer: replied 1 year ago.
What could the problem be? The boat would barely move in the water thought it was the prop clutch. I replaced it but did not fix the problem. I had boat out of water and started it in natural and it knocks real bad.
Expert:  Jason replied 1 year ago.

When you say you replaced the prop clutch. Are you talking about the clutch inside of the lower unit? Did you open up the lower unit and remove the propeller shaft to access this clutch? Or are you talking about the hub that is inside of the propeller?

Customer: replied 1 year ago.
The hub clutch.could it b the u joint or bearing? No have not taken the lower unit apart. Not sure where to start new boat owner.
Expert:  Jason replied 1 year ago.

Are you near the boat now? And is the boat in the water, or on a trailer?

Customer: replied 1 year ago.
Not near boat on trailer.
Expert:  Jason replied 1 year ago.

The most common problem that happens when ever there is a strike is the propeller shaft will bend. When the shaft bends, that throws everything out of balance. The specification on what is allowable is 0.010 of an inch. To word that, that is ten thousandths of one inch. What you want to do is kneel down next the propeller, and spin it by hand. If you can see any wobble at all in the end of that shaft then it will be bent by more than 0.010 of an inch, and it will need to be replaced. Does that all make sense to you?

Expert:  Jason replied 1 year ago.

I think that should do it. But I work for tips so I do want to make sure you are happy with my service before you go. If you had a further question on the issue by all means feel free to ask. If not, Just in case you do not understand the way the website works (and some folks do not). You do have to put forth a positive rating in order for it to credit me for helping you. When ratings are not done, the website simply keeps your deposit and they will not credit me. The ratings box is located at the top of the screen. To rate, you must select the star you wish and also confirm it. Please let me know if you run into any problems or errors when trying to do it. If you do have a problem, or if you can not see the ratings box which is at the top of the screen. Please reply back "I rate Jason's service _______" and fill in the blank.

Questions do not close out, so if you have to come back later on with follow up questions to the issue you still can even after doing a rating.

Thank you


Customer: replied 1 year ago.
Thanks for the help. But I guess ill just have to tar into it. I do machine work for a living and some repair work. It ha a hard ***** *****ke u joint out or bent drive shaft. Almost like broken connecting rod but motor runs knocks in neaurtural so it has to be before let goes in lower unit.
Expert:  Jason replied 1 year ago.

it knocks in neaurtural so it has to be before let goes in lower unit.

Not necessarily. When the stendrive is in neutral, the input shaft, and vertical driveshaft are always spinning, as is the pinion, forward and reverse gears. The only thing that is not spinning is the propeller shaft. However, depending on how the drive is angled, you can hear the clutch which is attached to that propeller shaft bounce around a little bit. Were you able to have another look at the boat since we last spoke?

Expert:  Jason replied 1 year ago.

Hi Kevin, just checking in. Have you had a chance to have a look at the lower unit?

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