milky lower unit oil

[jwmiller33]

the culprit: 1979 Johnson 35HP long shaft tiller (model: 35RL79A). Had this exact same problem last fall. Took it to a boat mechanic this spring and got a lot of work done, including replacing the seals (to fix the milky lower unit oil issue) as well as replacing the clutch doggy and the forward and reverse gear. i also got a new impeller put in as well.

the motor has run flawlessly this entire year. always starts up after a pull or 2. i used it a ton in the spring for a tournament (lots of prefishing and lots of miles on the motor), not so much in the hot summer months, and then i have been using the boat/motor a lot this fall... ive put a lot of hours on it recently as ive been trolling lead on mille lacs 4 or 5 times now, usually running the motor for a few hours each outing.

when i drained the lower unit oil, it turned out to be extremely milky, telling me lots of water had gotten in there. also, the past week or so i have noticed a couple (3-4) drops of very black oil on the garage floor directly underneath the lower unit. this oil is not milky at all, and i couldnt really figure out where it was dripping from, but it wasnt from the prop area, nor the 2 lower unit screws used to change the oil.

when i was letting all of the old oil drain out of the motor before i put new stuff in, i noticed a few drops of that very black oil starting to drop on the floor... i look, and there was a very good amount of very black oil (not milky at all) coming out of this hole:

as you can see, this oil is coming out of a hole that i dont think oil is supposed to come out of... my question is, what is this hole that the black oil is coming out of? and why is this oil black and not milky like all of the other oil i drained out of my lower unit? after watching a few you tube videos, i think it might be the shifter seal.. a guy had a similar problem on a motor he was fixing on a youtube video, same symptoms w/ black oil coming out of that same spot on the motor.

i didnt get any line or anything like that in my motor this entire year (since i got the seals replaced).. i never sucked up sand... i never hit rocks... i did however, hit a small log on pool 2 once at night, but i wasnt going that fast and i had the tilt lever switched up, so the motor just lifted out of the water and the log passed underneath... could that have played a part in one of my seals getting blown?

marineman-i am hoping you can help me out... i am dumbfounded as to why i have milky oil coming from the lower unit and very black oil coming from some other hole (which i may think might be the water exhaust or intake or something).

i am hoping to get in touch with my step dads boat mechanic tomorrow morning and see if i can bring it in to him tomorrow.. hopefully all that has to be fixed is the seals, and i can be fishing by this weekend!

[jwmiller33]

one more thing, i am trying to look up the seals on a boat parts HSOforum right now.. i think I found the right ones... are these the seals I need for this fix? are these all of the seals for the lower unit or for the entire engine?

[Surface Tension]

The black oil is residue from your exhaust and nothing to worry about.

The leak on the lower unit could come from a few places, the only way to know which seal is bad is a pressure test.

Prop shaft, hub, shift shaft, drive shaft, or as as simple as a leak from the fill or drain screws(bad washer).

[SkunkedAgain]

+1 There is obviously a negative leak there (allowing flow in) so a pressure test is the best diagnosis tool

[Ralph Wiggum]

I gotta ask. When you drained the oil, had you just used the motor? If so, I think it's fairly normal for the lube to look a little "milky". I like to check mine when it's been sitting for a day or so. The water will settle out and drain first when you pull the drain plug.

[jwmiller33]

Ralph, the motor has been sitting idle for about 5 days or so

[jwmiller33]

since i just changed the lower unit oil, would i be ok using the motor tomorrow and the day after for one last outing before i get the seals fixed? it seems to have been working fine all summer

my main worry is taking it out of the water over night in possibly freezing temps

[Surface Tension]

Use it and drain it when your done for the season.

[JohnMickish]

I would get water in mine every year. I had it re-sealed but it kept getting water in. Pretty furstrating to say the least. Turned out to be the top drain plug. I always changed the little gaskets so that wasn't it. Now I put a wrap of teflon tape (that thin white tape) around both plugs and just to be safe I smear some clear silicone over the top of them. No water for two years now.

I suggest before you spend the money to re-seal it, have someone pressure test it first. If the seals are good, there is no sense in replacing them.

[hamms-scooter]

JW,I had that black stuff as well coming out of my 15 hp and went in and asked about it and guy said it is from trolling and not cracking it open and letting exhaust burn it up. Before I leave to go to landing now I just crack it open.

[jwmiller33]

used the motor for about 6 hrs last night and about 5 hrs today and it worked just fine! i was afraid of the temps dropping below freezing last night so i just brought a little kit to change the lower unit oil quick after we took the boat out of the water at like 10pm last night. it took about 10 min and gave me piece of mind i didnt have water freezing and expanding in my lower unit over night. taking the boat in this week...

[benjineer]

Pull the prop off occasionally to look for fishing line. It is kryptonite for prop shaft seals. Even if you had it resealed and got some line in there, it won't take long to eat the seal up. Mine had been getting water in it for a couple of years. I finally had it resealed (and a bearing replaced) at the beginning of this season. I haven't pulled the plug since then. I also need to take my own advice and pull the prop, since I haven't done that since then either. I don't ever winterize mine, but I do pull the bottom plug and check for water before the first hard freeze.

[jwmiller33]

i pull the prop off about every 2 weeks or so throughout the summer and check for line, and I have not pulled line off my prop this entire year since I got it resealed. I am very cautious about getting line in there, and like I said, I take the prop off and check very often, so you can cross that off the list of possible culprits. Thanks for the advice tho benji!

[jwmiller33]

JW,I had that black stuff as well coming out of my 15 hp and went in and asked about it and guy said it is from trolling and not cracking it open and letting exhaust burn it up. Before I leave to go to landing now I just crack it open.

by crack it open, do you mean like bump it up to full throttle for a minute or so before you head in?