Topic: Shift shaft ”O” ring. installation technic on OMC lower units

This topic has 8 replies, 5 voices, and was last updated 6 months ago by aquasonic.

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May 22, 2024 at 11:53 am #287901
billy-j
Participant
US Member - 2 Years
When installing the shift shaft ‘O’ ring in OMC lower units What is the best method for success in creating a long-term seal. Is it best to install O ring and tapping retaining bushing till it bottoms on O ring then pushing shift shaft thru O ring. Or pushing shift shaft thru O ring then tapping in the retaining bushing with a section of pipe or tubing to bottom on O ring? Also is it proper to bottom the retainer on O ring? And finally, some lower units have a fiber washer installed with O ring and some do not seem to have fiber washer. Should the fiber washer be installed above or below O ring when it is installed in lower unit bore and what is the fiber washers function.
May 22, 2024 at 1:32 pm #287905
fleetwin
Participant
US Member - 2 Years
This is an interesting topic. I usually use the OMC tool, so the shift rod is not in place. But, there surely is a good argument for having the shift rod installed first through the oring to make sure it is oriented properly The next question is a great one as well. How far do you tap the bushing in. There is no spacer to bottom out on, in most cases, and driving the bushing in too far will probably distort the oring and lead to leakage. I usually try to make a note of how far the bushing was tapped in before removing it, and try to reset it to that position.

Some newer models have a bushing that encapsulates the oring and bottoms on that plastic spacer, this takes the guess work out of the equation for sure…

Once I have driven in the new oring and bushing, I usually take a grease gun to fill that cavity with grease before installing the shift rod…
May 22, 2024 at 2:55 pm #287906
crosbyman
Participant
Canada Member - 2 Years
I just remove the bushing intsall o-ring … re- insert the bushing tapper down against the o-ring …. polish the shift rod to remove any corrosion or roughness and slide it delicately down with some oil.

Joining AOMCI has priviledges 🙂
May 23, 2024 at 2:17 pm #287925
billy-j
Participant
US Member - 2 Years
fleetwin wrote:

This is an interesting topic. I usually use the OMC tool, so the shift rod is not in place. But, there surely is a good argument for having the shift rod installed first through the oring to make sure it is oriented properly The next question is a great one as well. How far do you tap the bushing in. There is no spacer to bottom out on, in most cases, and driving the bushing in too far will probably distort the oring and lead to leakage. I usually try to make a note of how far the bushing was tapped in before removing it, and try to reset it to that position.

Some newer models have a bushing that encapsulates the oring and bottoms on that plastic spacer, this takes the guess work out of the equation for sure…

Once I have driven in the new oring and bushing, I usually take a grease gun to fill that cavity with grease before installing the shift rod…

The grease is a good idea. Thanks
May 23, 2024 at 2:18 pm #287926
billy-j
Participant
US Member - 2 Years
crosbyman wrote:

I just remove the bushing intsall o-ring … re- insert the bushing tapper down against the o-ring …. polish the shift rod to remove any corrosion or roughness and slide it delicately down with some oil.

This is how I have been doing it. I just wondered what others did also. Thank You.
May 23, 2024 at 2:22 pm #287927
jeff-register
Participant
US Member - 2 Years
In the past I removed o ring , spacer & shift rod. Next I clean all mating surfaces, then lube the o ring & shift shaft & with inert lube &install shift shaft in the upper case then slide the o ring down the shift shaft until seated in the case. slide the retainer bushing down & tap into place. This way I can adjust the o ring tension with shift rod in place.
May 24, 2024 at 8:04 am #287937
billy-j
Participant
US Member - 2 Years
jeff-register wrote:

In the past I removed o ring , spacer & shift rod. Next I clean all mating surfaces, then lube the o ring & shift shaft & with inert lube &install shift shaft in the upper case then slide the o ring down the shift shaft until seated in the case. slide the retainer bushing down & tap into place. This way I can adjust the o ring tension with shift rod in place.

I am going to try your method next time I do a shift shaft O ring. What did you use for an inert lube? Another post said after he installed O ring he pumped some grease into the retainer/O ring cavity and I thought that was a good idea too.
May 24, 2024 at 2:10 pm #287952
fleetwin
Participant
US Member - 2 Years
OK, I do pump some grease in there, but after the bushing has been reinstalled. Filling that cavity with grease beforehand might loosen the fit between the bushing and gear housing causing it to slip back out of there…

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billy-j
May 25, 2024 at 6:42 am #287965
aquasonic
Participant
US Member
When reinstalling the bushing, tap the bushing down until the top of the bushing is flush with the bottom of the chamfer at the top of the opening. I had the same question. Frank Robb had the answer.

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billy-j
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Shift shaft ”O” ring. installation technic on OMC lower units

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