Logo
FULL SITE MENU

Lower Unit Oil

S

signal2noise

New member
"Hi all,

So I changed my l

"Hi all,

So I changed my lower unit oil a few weeks ago and have run the boat since then with no problems. This past weekend I was about to do some work at the transom and I noticed black oil over the entire skeg. I should have looked more closely, but I think it's coming from the hub itself not the lower unit fill or drain plug....based on lack of evidence of an oil track from the fill or drain port to the skeg.

When finishing the oil change I replaced the fill and drain plug. One of them was missing the o-ring seal! I was pretty confident that I didn't lose the seal...but you never know. I reinstalled the plugs.

Is it possible that this missing seal is the problem? Causing me to leak oil? I ordered replacement plugs and will change lower oil again with new plugs this weekend to see if that corrects the problem or if I have something else to trouble shoot (or if I need to get a mechanic for something larger that I can't or don't have time to do).

Thanks in advance."
 
"If the oil is black, it does&

"If the oil is black, it does'nt sound like lower unit oil. Oil leaks from the lower unit is usually light brown/clear color. What you're seeing is probably unburned engine oil coming from the exhaust. When you change the drain/vent plugs you'll see the lower unit oil, and if it comes out looking cloudy and/or milky, then I would worry about a leak in lower unit."
 
"Signal, Smell the black oil.

"Signal, Smell the black oil. If it stinks, it is lower unit gear oil. If it smells like gas or motor oil, it is fuel residue."
 
"Thanks Paul?

Which exhaust

"Thanks Paul?

Which exhaust - one near the skeg? My boat doesn't get as much use lately as it used to, so at start it looks like it burns a lot of oil....thick gray smoke.

Should I be concerned about this? Could it be using too much oil? Any suggestions on how to check this? I'm on the novice side of doing routine engine maintenance.

Thanks again."
 
"Joe is right, before you get

"Joe is right, before you get too far into this, knowing what motor you have may help. Generaly, pre-mix, if that is what you use,a motor will smoke at an idle/low speed more than it will running wide open. At idle the motor does'nt use the oil as it would wide open throttle (WOT). So it may be normal, but this does'nt mean that you should dismiss anything without checking to find out why any symtom shows itself."
 
"Thanks Joe! Thanks Paul!

I

"Thanks Joe! Thanks Paul!

I realized I didn't put the model number down or anything else identifying the engine. I'd have to be at the boat to get that info. I can tell you it's a 2001 Johnson, 115hp, VRO (not pre mix).

Here is a pic of the engine I found on craigslist.
http://mcallen.craigslist.org/boa/425846390.html

I'll be at the boat tomorrow, so i can get the info then.

Cheers."
 
"Loosen the drain screw on the

"Loosen the drain screw on the lower unit and examine the gearlube. If it is the normal coloring of gearlube rather than black, then I would think that you could safely assume that the lower unit seals are okay.

You can check the lower unit by draining the gearlube, replacing one drain/fill screw, then pressurizing the unit with air 7 to 12 psi, no more than 12 psi. This would reveal any leaks by sound and/or sight.

Usually a "Black" oil coating is just the unburnt mixture running/dripping down thru the soot coated inner exhaust housing "BUT" it's a good idea to check to make sure."
 
How do you pressurise the lowe

How do you pressurise the lower unit as I will be checking mine in spring. 20 johnson 84 not thru prop exhuast.
 
Use a air compressure set to t

Use a air compressure set to that low setting. A small short piece of fuel hose between the lower unit and the air nozzle will do the trick.
 
I changed the lower unit oil a

I changed the lower unit oil again late last week. It didn't look lie it was the problem as the oil seemed full (though it didn't leak out of the vent hole when I opened it)

I installed two new drain and vent seals during the change.

I'll keep my eye on it for now and assume it was unburnt oil.

Thanks you all for your help.
 
Back
Top