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Hard knocking-noise when accellarating or trimming Alpha One Gen One - U-joint?

C

Crestflite

New member
Dear community,

I am really frustrated when it comes to my '77 Glastron V184. I bought it two years ago with a damaged motor and installed a used 5.7 Mercruiser (which was installed before, too). Originally, it was equipped with a 5 liter Ford, but the previous owner exchanged it with the 5.7 GM and put in also a Alpha One Gen One outdrive but kept the pre-Alpha transom which all worked out fine.

Now to the problem:
The engine runs fine on muffs, is perfectly aligned and I could turn it when in gear without any noise and could also trim it up without any noise even when I rev it up. As soon it is in the water and in fwd gear, there is a loud metallic knocking sound when accelarating only little or when I trim it up a little.

My mechanic is specialized on Mercruiser outrdrives and has checked the outdrive. He says it all looks fine including the gimbal bearing and(!) U-joints.
The fact, that the noise comes when I trim the outdrive a little makes me think that it could still be a defective U-joint. I also thought about rotten stringer or transom so that it is no more alignment when I rev it up in gear but it would make no sense that when tilting a little there is this noise, too.

What do you think?

I am really looking froward hearing from you.
 
my thought is thoere is an issue with a bearing in the outdrive. on land there is no load, as soon as you put it in gear on water you get a noise. Would drain the lube and look for signs of metal maybe pull the top cap.

Ujoints are easy enough to do when the drivew is off. MOOG 315G will fit your drive you can feel the gimbal bearing whennthe drive is off to check but I'm assuming your mechainci did this. Rotten stringer or transom would show in the alginement was that checked
 
Dear Dieter,

thanks for your reply.

Yes, my mechanic has checked the gimbal bearing and says it looks good. The alignment was checked before I changed the rear engine mounts (two bolts with the fiberglass washer) and it was good. After I installed the washer and spring, we aligned the engine again.

My mechanic also opened up the top cap of the outdrive and inspected it for wear and tear - nothing to see. But what I recognized is, that when I changed the impeller two weeks ago I found some metal abrasions (little) at the magnetic drain plug. I think that is normal, isn`t it?

Thank you for the hint with the MOOG Universial joints. They are much cheaper than the "Mercruiser" joints I have ordered two days ago. Are you quite sure that they fit? I haven't found any link to Mercruiser.
 
Are you sure your issue isnt a shift issue.

If this occurs when trimming up is your forward gear engagement having issues and what you are hearing is the clutch dog teeth hammering when trying to re-engage?

It is rare but just a shot in the dark as you have no video with sound to judge what the issue may be
 
Crestflite said:
Dear Dieter,

thanks for your reply.

Yes, my mechanic has checked the gimbal bearing and says it looks good. The alignment was checked before I changed the rear engine mounts (two bolts with the fiberglass washer) and it was good. After I installed the washer and spring, we aligned the engine again.

My mechanic also opened up the top cap of the outdrive and inspected it for wear and tear - nothing to see. But what I recognized is, that when I changed the impeller two weeks ago I found some metal abrasions (little) at the magnetic drain plug. I think that is normal, isn`t it?

Thank you for the hint with the MOOG Universial joints. They are much cheaper than the "Mercruiser" joints I have ordered two days ago. Are you quite sure that they fit? I haven't found any link to Mercruiser.
Click to expand...
Im fairly certain the moog 315 will fit your drive, but the advice is worth what you paid for it....here is a link from another forum with that info https://forums.iboats.com/threads/u-joint-part-number.235294/

you can find moog315/equivalent dimensions on line measure them vs yours.

Yes a light dusting of metal on the drain plug magnet is normal for a dog clutch MC-1 /R/MR/Alpha drive

Id hate to just replace parts but based on what info you give I'd do the gimbal bearing and ujoints. Hopefully you can return the 'marine' ujoints and go wiht the $15 autoparts store ones....
 
Crestflite said:
Dear Kghost, dear Dieter,

I haven't thought about a shift issue or about the dog teeth but that is really something I or better my mechanic will take a look at.

I have now uploaded two videos on youtube:

https://www.youtube.com/watch?v=b1fRfYSZiow

https://www.youtube.com/watch?v=TBN9mzOl1GM
Click to expand...

I think you need to determine where the noise is coming from to me that sounds more like an engine noise. I did see a Utube video where a guy posted a similar noise on a merc 5.7 and it was a blown head gasket leaking water in to cylinders

https://youtu.be/HRyOwnhQwgE

Maybe worth a check for water or compression check
 
The engine runs very good when in idle and even when I rev it up without beeing in gear. The engine is sound and compression is good and almost even on all cylinders. No noise apart from a rattling waterpump.
Secondly, the noise comes up especially when I trim up the outdrive just a little or when I accelarate when in fwd gear. I am pretty sure it is somthing from the outdrive.

But thanks for watching the videos! Really appreciate that.
 
You need to remove outdrive and check all parts again.

Check o-rings on input drive shaft, two, which sit in the gimbal bearing and make sure they are there.
YOU need to stick a couple fingers into gimbal bearing ans spin it to see if it is smooth turning, If it is not then that may be your issue.

Look closely at input shaft splines and there should be nothing but grease, No metal at all.
 
Crestflight, did you ever determine what was making the sound? I have a Mercruiser 140 presenting the same issue, I am very interested to know what you find... thanks
 
sixty-seven said:
Crestflight, did you ever determine what was making the sound? I have a Mercruiser 140 presenting the same issue, I am very interested to know what you find... thanks
Click to expand...


I have renewed the U-joints but with no effect. Really frustrating. I noticed that during hard turns it is quiet in my engine compartment/outdrive. I now suspect that the gimbal bearing is not fully seated. Tomorrow, I will replace the gimbal bearing and will report to this forum whether the noise is finally gone. I really hope so.
 
Sounds like a stick stuck into a fan blade. Get a cheap stethoscope from Harbor Freight; you can detect noise on any non- moving part of the engine.
 
Crestflite said:
I have renewed the U-joints but with no effect. Really frustrating. I noticed that during hard turns it is quiet in my engine compartment/outdrive. I now suspect that the gimbal bearing is not fully seated. Tomorrow, I will replace the gimbal bearing and will report to this forum whether the noise is finally gone. I really hope so.
Click to expand...
did you ever fix the issue. Have same problems, u-joints,gimbal and coupler all good.
 
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