oil leak 7.5 Johnson

[SPK]

The parts booklet diagram on the Johnson 7.5 AD 12 1958 shows the O ring closest to the prop, followed by the seal. So the diagram appears to be showing that the seal would go on first, followed by the O ring. Is that correct? Is that the right assembly order? I have the O ring but not the seal.

I have a minor leak of lower gear oil that appears to be coming from behind the prop, maybe a spoonful in the course of a day.
Would replacing the O ring help resolve the problem or is it more likely that the seal is the culprit?
How do you replace either or both of these parts? I think I can do it I just don't know how.
Thanks,
Sean.

 

[Daviet]

Re: oil leak 7.5 Johnson

The o-ring actually goes around the bearing Assembly that the seal goes into.

 

[SPK]

Re: oil leak 7.5 Johnson

Thank you very much for the reply but I am still unclear if the gearcase has to come apart to install the o-ring.
Would you mind clarifying this for me.
Thanks again,
Sean.

 

[Daviet]

Re: oil leak 7.5 Johnson

Yes, the lower half of the gear case (skeg) has to come off to remove the the bearing housing to replace the propshaft seal and the o-ring. Most of the time a person would pull the complete lower unit and then seperate the lower unit on the bench, but it can be done without removing the complete lower unit. It is a good time to check/replace the water pump if you remove the lower unit.

 

[SPK]

Re: oil leak 7.5 Johnson

Thanks very much. I just did the impeller a couple of days ago and found it not to be too difficult. I just took my time and worked carefully.
Do you suspect that the o-ring is causing the leak or is it more likely to be the seal?
It is a minor leak, maybe a spoonful in a 24 hour period but it is still a leak.
I am somewhat concerned as to whether removing the lower half of the gear case and reassembling it might result in yet another leak. There is no leaking at that point at all right now.
What do you advise?
Sean.

 

[Daviet]

Re: oil leak 7.5 Johnson

My GUESS is that the seal is giving you the problem. Have you pulled the prop and see if you might have some fishing line or something around the prop shaft getting into the seal?
If I were going to do the repair, I would pull the lower unit and reseal the lower unit. Sierra shows a complete reseal kit for your engine, PN 18-2679.

 

[reddogg]

Re: oil leak 7.5 Johnson

Could be either or. Last time I had a leak I thought it was the propshaft seals and it turned out to be the o-ring If your gonna have it torn down, i'd go ahead and replace both than pressure test before you put it back on.

Red