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Lower drive shaft play

Johnny340

Johnny340

New member
I have a vibration in gear at idle. It goes away at higher RPM. I pulled the drive today expecting either u-joints or gimbal bearing issues and both feel perfectly fine. The lower driveshaft however, seems to have excess side to side play. See video. I wondered if this was normal or if perhaps the mid bearing was no good. I have 230 hours on it.
Thanks in advance!
 
Yes, I have the 'carrier assembly' and the 'retainer nut' removed so it is only held by the bearing. When I pull up on the shaft the play still seems to be the same. Does this look excessive?

I also used an alignment tool to check the engine alignment and it goes in ok but definitely shows more grease contact on one side than the other. Would this be enough to cause a vibration?
 
If the vertical shaft has issues you more than likely would have had gear damage.
put it back together then pull up and see.
If you have ever set up a lower gear case you would know the process to check gear lash, you have to use special tools to pull shaft up.
Wrong place fo be looking for vibration as you describe

If alignment is good it is good.

If not a bad gimbal bearing or ujoints the most likely issue is the prop shaft or propeller.
 
Thank you for the reply. I agree this bearing seems like a low probability for failure. I don't have the complete set of specialty tools to remove it anyway. I understand the backlash and feel the amount is normal. It was just the side to side play through that bearing I was concerned about. I think I'll put it together with a new carrier assembly (plastic conical part with o-rings) and check the prop shaft for runout next.
 
OK, so the prop had a 10 thou runout at the end which I suppose could cause this vibration at low rpm. Any recommended DYI methods to take this out?
 
Johnny340 said:
Thank you for the reply. I agree this bearing seems like a low probability for failure. I don't have the complete set of specialty tools to remove it anyway. I understand the backlash and feel the amount is normal. It was just the side to side play through that bearing I was concerned about. I think I'll put it together with a new carrier assembly (plastic conical part with o-rings) and check the prop shaft for runout next.
Click to expand...
Once upper is installed there is NO side to side...
 
Johnny340 said:
OK, so the prop had a 10 thou runout at the end which I suppose could cause this vibration at low rpm. Any recommended DYI methods to take this out?
Click to expand...
Yes, bring it to a marine tech who has all the tools as the vertical shaft has to be removed to get prop shaft out.

If you know a machinist with a good lathe the prop shaft can be straightened with a good lead hammer. No mord than .003 at taper area on prop shaft where prop section begins
 
OK, so the runout was roughly 10 thou at the end of the threads but only 3-4 at the taper area so maybe it's ok. The play on the vertical shaft is minimal when pulled up.
I think I'll try a new prop because this one is suspect anyway. This one has a serial number that ends in 21 which I assume is a 21 pitch. I'd like a little more out of the hole and figured a 19 would be a good compromise. Thoughts? It's a Fourwinns Horizon 180.
 
If they look to be 10-32 size they are for a sacrificial anode that bolts to the end of the carrier,
 
Ahh. Makes sense. Thank you.
Thinking about getting a 14x19 four blade SS Prop to replace my 14.75x21 three blade aluminum one. Thoughts on this getting a little more pull without a huge top speed loss?
 
Johnny340 said:
Ahh. Makes sense. Thank you.
Thinking about getting a 14x19 four blade SS Prop to replace my 14.75x21 three blade aluminum one. Thoughts on this getting a little more pull without a huge top speed loss?
Click to expand...
If your vibration is in gear i would try swapping props before taking drive apart. Prop nick or damage is more likely…

what was your wot rpm with the. 3 blade 21? I prefer to run 4 blades for hole shot planning speed and stern lift. I actually get better top speed with a 4 blade revolution 4 as i can trim out fully. If your 21 was vlose to the top end of wot i would try a 20” like michigan vortex 4 blade. If ykur wot rpm is lower drop to a 18” or 19” . If you have a local marina or prop shop that will let you try a few that is even better
 
So that Turning Point prop (14x19) was perfect for this setup.
As for the vibration, it still exists at very low RPM especially when activating the trim. Even selecting trim down when it is already fully down will cause this vibration for a few seconds. Prior to this outing, I checked the gimble bearing and u-joints which felt perfectly smooth. Plus a new prop. The engine has 250 hours on it. Is it possible the coupler could cause this vibration?
 
Thanks for the response Guy. I have a brand new prop but there was a slight runout on the prop shaft so maybe that was the problem.
 
.003" at taper at seal.

But a wobbling prop will ressinate thru boat regardless of spec.

Get shaft straightened and be done with it!
 
Yes .003 (which is considered in spec) but the threads were out more. The new prop and hub is riding on the part in spec and it is hard to measure the actual threads. I would think the tightened nut would keep the prop aligned correctly but I guess if the threads are out then that could make the whole shaft seem out?? I'll have to take the lower end to someone with the special tools. Sounds like a job for the off-season.
 
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