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1987 4.3 Mercruiser/Alpha One outdrive pinging when running

E

evinrude_boater

Member
An irregular pinging sound is coming from the outdrive when running. The U-joints are in good condition, well greased, no sign of moisture or rust and very easy to move. The gimbal bearing is well greased as well and turns smoothly. Could a bearing in the outdrive make this sound? I don't want to open it looking for something without knowing what to look for. Is there any disassembly that I can do without specialized tools? Please have a listen to the video at the drop box link below. https://www.dropbox.com/s/94t0jmxw7y9s5hr/20160710_155607.mp4?dl=0
 
I ran the engine without the out drive and there is no sound from the engine alone. I took the top cap off the outdrive and the gears are undamaged from what I can see. From watching videos from other boaters it seems like the sound is similar to U-joint problems. Can anyone describe U-joint noise?
 
Possibly the exhaust flappers...just below the rubber tubes on exhaust where the long vertical aluminum exhaust tubes go to transom.

If the rubber coating on the flappers goes away the remaing metal will sound like pinging...
 
kghost said:
Possibly the exhaust flappers...just below the rubber tubes on exhaust where the long vertical aluminum exhaust tubes go to transom.

If the rubber coating on the flappers goes away the remaing metal will sound like pinging...
Click to expand...

I thought I ruled that out by running it without the outdrive and the sound wasn't present. I initially thought it was the flappers when I fired it up and I heard the pinging before water started to exit the prop.

Can I wiggle the elbows off without removing the manifolds by loosening the rubber couplers?
 
Last edited:
You can, with some finesse, remove the rubber boots/tubes without removing anything else........but the boots/tubes.

Pull them towards the elbows and try to pry them away....to expose the exhaust tubes and flappers.


Only way to rule it out.........
 
I removed the outdrive, split the cases, checked the water pump, spun the shafts by hand, took apart one U-joint and found nothing out of the ordinary. Put it all back together and ran the engine on muffs. There was no noise for 15 minutes of running then it started pinging again for about a minute then went away again. I checked the engine bay while it was pinging and I couldn't hear it there. To me it seems the loudest at the bottom gear case but the prop shaft wasn't turning.
In attempts to see if it's the U-joints I raised the outdrive while it was running in neutral at an idle and turned it from side to side and the pinging didn't return. I'm a little mystified as to why it comes and goes.
Here's the latest video close-up to the outdrive. https://www.dropbox.com/s/mx5g958odliuaxu/20160714_111541.mp4?dl=0
 
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