87 4.3 Merc outdrive pinging

[Evinrude Boater]

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/mx5g958odl...11541.mp4?dl=0

 

[Rick Stephens]

I would get u-joints at your local auto parts store and swap em out. Too inexpensive to not replace. Last noisy ones I had still in my shop because I can't see anything wrong with them I take em out and look at em now and then just to see if I can figure out why they made so much noise.

 

[Pete104]

I wouldn't do anything with u-joints.
Disconnect the intermediate shift cable after the noise returns. Running it like you have, on the hose, in the shade, ya-da ya-da. When the noise comes back, gently push the cable until you hear the noise then pull back on it. I'm thinking your shift cables aren't adjusted properly & the clutch dog is killing itself trying to do something.
Do this with clear area behind the boat! No kids, dogs,wives or even ex-wives. The drive can go go into gear while doing this. But do it slow and it won't.

achris has a video on how to dial in the shift cables.

 

[Evinrude Boater]

I found the video on YouTube. Are you thinking the shift dog is trying to put it in gear because the cable is out of adjustment? It's not the usual clicking sound when someone eases it into gear instead of shifting quickly.

 

[Pete104]

Yes, but no. I'm thinking the clutch is not centered between the fwd & reverse gears. And that comes down to cable adjustment plus a healthy shift system. The weakest link in the shift system is the "shift spool". It's connected to the clutch dog thru the propshaft. There is specific troubleshooting guides in the appropriate service manual. There is also spec on the spool, I wanna say it's .004"-.010". Along with splines on shift shafts that corrode or get sloppy.
What I'm seeing & hearing is the clutch dog bouncing back and forth between the gears. At the very end of the video, you see the slightly turning as the noise picks up. The angle that the drive is on makes believe the clutch dog is sliding, in this case "down" the propshaft into the reverse gear. Don't forget, the boat is out of the water & you hearing things you don't in the water. My main concern is that the drive shifts properly. While in the water does the drive go into gear & shift out of gear without any issues. Typically the spool will give you a struggle to get out of gear. If you aren't experiencing any issues, then don't do anything. I you aren't comfortable with the noise fix it.

Repairing/changing the shift spool is a total tear down. If you are mechanically inclined & you will need special tools, you could handle this repair. Torques are more but not any worse than doing u-joints.

Just so you are clear. With engine running the fwd & reverse gears are turning. When you move the shifter handle the clutch dog is not moving until it comes in contact and fully engaged in respective gear selected. It's not good practice on slow shifts or just letting the dog bang like it is.

 

[Evinrude Boater]

Pete104, it doesn't shift from forward into neutral easily. I generally have to go past neutral towards reverse to ensure it shifts into neutral.
If I run it in gear is the sound going to stop if this is the cause? My recollection is that it pinged in gear as well as neutral but I can verify it.
If I trim up the outdrive will it spin the prop in reverse as the clutch dog slides the other way on the shaft?

 

[Pete104]

I watched video again and the prop wants to go fwd. So disregard the clutch dog falling backwards into the rev gear. But the centering issue is still there.

You definitely should not have to go past neutral to obtain neutral. Do you know if the shift interrupt switch is working? Or ever has worked? Shifting without it will cause issues that I'm looking at.
Yes, you won't hear the tap-tap, tap-tap pinging (as you titled) when fully engaged in gear. The clutch dog is fully seated in the gear.

Mercury had some problems with shift spools back around '86-'87. They blamed the failure on boat builders & dealers. It took them 2 years to produce a fix, of which they still use today and to their credit payed dealers a little to fix it. And also redesigned the shift spool itself. Read this service bulletin # 89-4
http://www.boatfix.com/merc/bullet/89/89_04.PDF It covers alot of info.

 

[Evinrude Boater]

I think Pete104 had the correct diagnosis. I adjusted the shift cables and there was no more pinging inside the drive. The 6" adjustment was off by about 1/4". I ran it for about a half hour on the muffs and no pinging. Hopefully it shifts better in the water. Thanks Pete.

 

[Pete104]

Enjoy!!!