Knocking noise in back of engine. Help!!!!
 

I took my boat out on the lake for the first time and I have a knocking noise that seems to be coming from the back of the engine or top of the outdrive. I purchased this boat, 1996 Talari 201, 5.7 L, Alpha One-Gen II, about three months ago and have been working on it since I purchased it.The majority of the work has been to improve the looks (badly oxidized) and fix the little mechanical/electrical problems that it had. Also, refurbish the trailer. I noticed this noise when I puts the cuffs on the outdrive and ran it it my driveway, but it didn't seem as bad as it did when I put it in the water. It sounds somewhat like a rod knock, but I know that it is not in the engine, because there is no change in sound when you rev the engine. Also, in reading about gimbal bearings on the site, there does not seem to be any change in the sound, when the steering is moved from full left to full right. The sound is not a growl or a whirr, it's a knock or clunking sound. Also, there is no vibration when running on the lake. It runs very smooth and comes right up on plane and trims out just fine. Any advice on this will be greatly appreciated.

Re: Knocking noise in back of engine. Help!!!!
 

hi Tom,

My thoughts are that your u-joints are beginning to fail and need replacement. While you (or your mechanic) have it apart, i would suggest replacing the gimbal bearing too.

Re: Knocking noise in back of engine. Help!!!!
 

I didn't think that the u-joints turned unless it was in forward or reverse. This noise is happening when it is at an idle, in neutral.

Re: Knocking noise in back of engine. Help!!!!
 

The U joints are turning whenever the motor is running but as Mikey suggests...it could be the gimble bearing as well. While you have the outdrive off, check the operation of your trim sensor and limit switch as well. If they need to be replaced...that would be the time to do it.

Re: Knocking noise in back of engine. Help!!!!
 

What should I expect, in costs, if I had a mechanic replace the gimbal, two u-joints and all of the hoses and bellows on the outdrive. I'm pretty mechanically inclined, is this something a person should tackle or should I take it to a mechanic? How many hours does it take to complete the job?

Re: Knocking noise in back of engine. Help!!!!
 

This is only a somewhat educated guess on my part but i would expect somewhere around $1500. Trying to do that job yourself will likely take an entire weekend unless you are really mechanically inclined & have all of the necessary tools.

I would suggest however that you read this thread by 'Chaddy'. Its a job likely best left to a proper mechanic.

And yes as Steve noted.... that is also the time to replace a failed trim/tilt sensor on the outdrive as the wires are run thru the outdrive boot to the trim motor.

Re: Knocking noise in back of engine. Help!!!!
 

Its a straight forward job- with the right tools.
I have done all of the above(plus or minus a thing or two) to two boats this spring. Both 7.4 Bravo 1. Did the bellows and u joints on an alpha as well. The tools are the key! YouTube the process, see if you think you are up to it. An extra set of hands can be nice.

With that noise check your drive oil level. Just a thought.
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