Replace Lower Unit Seals?

[Jefro573]

Hello All, fairly new to this boating stuff and need the opinions of others with more experience. I have a 1998 Force 120 HP OB. I am in the middle of replacing the Impeller and I was going to replace the Lower Unit Seals as I noticed chocolate milk substance coming from the exhaust by the prop and a hole in the lower unit by the water intakes. When I removed the lower unit there was this same substance all over the Impeller Housing and the exhaust cavity. When I drained the Lower Unit oil I didn't notice any water either. With that being said does the milky substance over the impeller housing mean I have a different/bigger issue? I am wondering if I even need to replace the lower unit seals at all? I have not done a pressure test on the lower unit. Any thoughts?

 

[racerone]

That sludge is very common on a 2 stroke motor.----Just unused oil from the fuel oil mix.---Very noticeable after running on a hose or after long periods of idling.----Possibly check your thermostat too.

 

[Jefro573]

Oh ok, so my Lower Unit may not have a bad seal after all. Is the only way to test the lower unit for leaks is by pressure testing? So the fact that it got into the exhaust cavity and out by the prop is ok? Its not hurting anything?

I have the water pump housing off too, I haven't removed the drive shaft or bearing carrier yet, so I am wondering if i need to go any further? Can i just put the water pump housing back on and the new impeller (with new gaskets of course) and fill it with new gear oil and I should be good to go?

I really appreciate your help...just might have saved me a lot of work if I don't need to proceed anymore.

 

[pnwboat]

If you have water in your lower unit, the first thing you will see coming out when you drain it is the water mixed with the oil. The water is heavier than the oil so it settles to the bottom. If you don't see any evidence of water when you drain the oil, you should be OK. I doubt you have a lower unit leak. Like Racerone said, most likely fuel/oil mixture that you're seeing from the exhaust cavity. Just refill the lower unit with oil and you should be good to go.

 

[Jefro573]

Yeah it was nothing but oil that came out of the lower unit from what I saw. OK, I will move forward with just the impeller replacement with new gaskets and see what happens. Just so I know, what should I look for as a sign I do have a lower unit leak just in case?

 

[racerone]

???----It likely was oil / sludge from the exhaust housing !!-----This is quite common.---But you seem confused by the concept.---Pressure test your unit if you feel this oil came from the lower unit / gearcase.--Guessing does not work here and testing does work.

 

[Jefro573]

No, I get it. All the places I saw this sludge is connected to the exhaust. I was just merely asking if there are any signs I can keep an eye out for in the future that indicates a lower unit leak. I will pressure test the lower unit before I put oil back in just to be sure. I agree, guessing doesn't work. Last thing I want is to go through all of this and put it back together just to find out I do have a leak.

 

[gregmsr]

Run it on the water a couple times with fresh lower lube then drain it again.
Be very observant when you drain it and look closely....
Don't freak out if there is a small amount of lightly colored milky lube..at least I don't.
Just keep an eye on it if it gets worse..and change it a couple times per season.

 

[jerryjerry05]

Sludge. Where you indicate.It's not normal.
In fact I've seen it only once in 30 years.
And that was an I/O OMC that had a gear oil leak.
The unburned oil/gas is mixing with the exhaust.
It sounds like you've got a gasket leaking somewhere.

The lower unit if it has clean grease is ok.

 

[Jefro573]

Update. I put the new impeller on and all the gaskets and tested the pressure from a homemade pressure tester I built and pumped it to 20 PSI. Its held there for 5 minutes now so I think I am good with the lower unit. Correct? It doesn't need to hold any longer does it? I shouldn't pump it any more than 20 PSI right?

 

[jerryjerry05]

No I usually only go to 12-13#
At 12 it should hold for a long time.

 

[Jefro573]

OK great. Thank you again everyone for your help. Saved me a lot time. I'll finish up putting back together the lower unit, fill with clean oil then move onto cleaning up the carbs and look into going to a 2 battery set up.

 

[Jefro573]

Well figures, I can't get the prop to go into gear correctly. The prop will spin in forward but will click with each turn. If its in reverse the prop moves barely but didn't want to give it much force. So I know its not lined up correctly. Is there a trick to getting it to line up correctly? I have the lower unit off again and was turning the prop and the shift shaft at the same time to try and get it to catch.

 

[jerryjerry05]

Drop the lower.
Put the shifter in F.
The shift shaft sticks through the front of the lower/top.
Turn it to the left as you lift up on the right prop blade.
This should put it in F.(if it doesn't turn the driveshaft as you lift up , turn the shift shaft the other way)
Your putting the lower in F gear.
This should work as long as you don't turn the prop the other way.Turning it the other way
will take it out of gear and you'll have to turn the shift shaft again.
Then lift it up and try to put it back. As you lift keep turning the prop lifting up on the right prop ear.
This will keep it in gear and turn the shaft aligning the grooves.

Hope you understand.

 

[Jefro573]

Ok. I gave it my best shot. Here is where I am. If I turn the drive shaft my hand (really hard to) the prop moves to the right (looking at the prop) which is forward, correct? But if I turn the prop to the right just by the prop there is a click with each turn. That means it's still not in gear correctly right? I've never turned the prop by hand when in gear so please excuse the dumb questions.

 

[racerone]

Likely that is very normal and nothing is wrong.

 

[Jefro573]

Well I'm not so lucky. Still not lining up correctly. So had to remove LU again. It's off right now and prop can spin freely. When I move the drive shaft in either direction ever so little it engages the prop in both directions. So my question is what gear is the LU currently in?

 

[Jefro573]

Update. That must have been the correct one. I put the LU on today and started up the boat. Went into F and R just fine with the prop spinning correctly in each gear. It was spitting to so new Impeller works. Thanks for everyone's help. I really appreciate it.