Lower unit oil leak

[Fiddlefire]

Hi all, I have an oil leak coming from the bottom of the lower unit from the prop area. I studied the lower unit area on a diagram it seems that there is a O ring type gasket that could be bad. I ordered one thinking that this might be the problem since I have not pulled anything apart yet. Are there any suggestions towards this process that I need to be aware of?
MN# of motor 70EL76D. Any suggestions would be helpful.

 

[Vic.S]

Are you sure it's not just unburnt oil from the fuel? That is the most common cause of oil leaking around the lower unit.

Have you checked the lower unit oil for signs of water intrusion. If no water ( milky looking oil) it's unlikely to be the gear oil that is leaking

The O ring is not likely to leak unless it has been disturbed

 

[Fiddlefire]

I'm pretty sure that it's a bad seal because it's coming out at the bottom of the prop only and it smells like gear oil and is grey in color indicating water mixed with oil. I had a few buddy's that are familiar with outboards and that was they're first opinion.

 

[Vic.S]

If you are pulling the bearing carrier to replace the O ring it might be a good idea to replace the oil seals also.

 

[Tim Frank]

OK, never mind Vic; he gets too wrapped up in that methodical troubleshooting stuff.
If you are " pretty sure" it is that seal just
order up the parts to do a R&R on all seals in the lower unit.
If it is your first time doing it you should be able to get through it in ~ 2-3 hours.

If that does not solve your problem you can still do Vic's 5 minute FREE check; but no point starting with the easy stuff.

 

[Lewis1111]

Grey doesn't usually indicate water in the oil....Milky looking oil would indicate water. 9 times out of 10 that oil is un-burnt 2 stroke oil from the exhaust. Pick yourself yourself up a cheap pressure and vacuum tester and test the gearcase the proper way for any leaks. You'll need this tool any way after replacing any seals or orings to ensure everything went back together the way it should.

 

[Fiddlefire]

Okay to narrow down the confusion. What I was calling an o ring was the two seals shown in this drawing (#28 quantity 2) is what I was lead to believe may be my problem. I watched a tutorial on you tube of how to replace them and looked pretty straight forward. Just make sure not to nick the prop shaft. They also stated that fishing line caught around the prop could also damage these seals as well. What I am going to do first is check the level and for discoloration from the top screw. I guess checking that first might be a good idea. I bought the gear oil and the pump for the job to do a fluid change. And where can I get one of those pressure gauges from ? That may also be helpful.

 

[Vic.S]

Okay to narrow down the confusion. What I was calling an o ring was the two seals shown in this drawing (#28 quantity 2) is what I was lead to believe may be my problem. I watched a tutorial on you tube of how to replace them and looked pretty straight forward. Just make sure not to nick the prop shaft. They also stated that fishing line caught around the prop could also damage these seals as well. What I am going to do first is check the level and for discoloration from the top screw. I guess checking that first might be a good idea. I bought the gear oil and the pump for the job to do a fluid change. And where can I get one of those pressure gauges from ? That may also be helpful.

The two seals are far more likely to leak than the O ring.

But check the condition of your oil. It should remain "clear and bright " If it goes milky looking that is the time to be concerned because it indicates that water is getting in. If the oil shows no signs of water intrusion there is no need to do anything about these seals , the drive shaft seals or the shift rod seal. Relax and go boating.

If you do have to replace any of these seals note the pair fit back to back so that one keeps the oil in and the other keeps the water out.

 

[Crosbyman]

agree with Vic....

start simple

drain the gear oil to see if it is pure oil (dirty a bit but pure oil) or a creamy coffee looking milk shake

if the gearcase oil is ok just go boating and save yourself time and money

if the oil is milky time for a reseal and shopping for parts

 

[Tim Frank]

^^^^
That is what I meant.
You 'd have to drain the oil anyway if you are doing a reseal, so why not do it first so that you know if it is really necessary.

 

[Fiddlefire]

Well as I stated before what I see is a milky color oil and it is coming directly out of the bottom of the prop and nowhere else after I run the motor on ear muffs. I'm going to unscrew the top screw and stick a long tie wrap in the lower unit sort of as a dip stick method to see what color it is. I will try and do this this weekend. If you don't hear results from me for a couple off weeks it's because my company is sending me to Bermuda for two weeks on Tuesday. I will certainly keep you posted once I get on it. Film at 11 !

 

[Crosbyman]

should tell you something but water sinks oil floats so open the lower screw

after a while water would separate and sink down

 

[Tim Frank]

^^^^^ +1