Lower Unit Leak?

[mrwglo]

I think I have an issue with my lower unit. 1994 Force 90. I looked at it the other day after the boat sat through 2 consecutive nights of single digits. A greenish oil was leaking out of the propeller area. Not a lot maybe a tablespoon full or so. Is this a problem and is it related to the cold? Could it have just leaked for that cold period and everything came back together ok? I ran it both days this weekend (I know Frank will yell at me for this) without trouble but I'm going to drain the oil and look for water sometime this week. Thoughts?

 

[Frank Acampora]

Re: Lower Unit Leak?

Let's see if I remember: You have a dual exhaust lower unit and you have been running double oil. The oil is usually either blue or green BUT The synthetic lower unit oil in it is green also. FIRST smell it. Lower unit oil has a VERY distinctive odor--smell it once and you will never mistake it again.

Your dual exhaust will drip some motor oil down into the prop area and it can drip out so it could be used engine oil. AGAIN, smell it. Engine oil will smell a bit like gasoline. Lower unit oil will smell "heavy" and sulphur reminiscent.

I don't think cold weather will make seals leak, but you never know----

If it is lower unit oil, then you probably have a leaking seal in the spool. It is easy to remove the spool and replace the seal but it requires draining the lower unit UNLESS you can tilt the engine almost horizontal. Of course, If water has gotten into the gearcase, then you would change all the oil anyway.

So: having run the engine--this weekend was nice; if I didn't have work to do at home, I would have been on the Chesapeake--now remove the drain plug after letting the engine sit vertical for a day or two. If there is free water draining first, or if the first oil out is cloudy-milky, then water has gotten in. If the oil still looks good, close it and top off with synthetic. You will probably be good for the season.

 

[mrwglo]

Re: Lower Unit Leak?

You remember correctly. It is definately lower unit oil as I also have the engine oil coming out of the upper exhaust. The engine oil is black and has a gas-like smell. The LU oil is light green color like pistachio pudding (is this the color it is supposed to be or is it supposed to be a darker green?) and has a distinct acrid odor to it. I pulled it out of the water and parked it in the yard, tilted the motor to vertical, and it only took about 10 minutes for the oil to be visibly leaking.

I'll drain the oil sometime at the end of the week as it is going to rain for a few days here. If I have water in there, I'll have to change the seal then, yes? Otherwise, I can just live with the leak and be sure to keep it topped off over the course of the season. Are there operational signs I should associate with this issue?

(off topic question, is it bad for some air to be in the fuel filter you installed? I haven't fixed the cracked fuel fitting yet and wondered if that was the culprit)

As always, thank you Frank!

 

[Frank Acampora]

Re: Lower Unit Leak?

That's a shame! When I changed the lower unit oil, the original oil was good so there was no evidence of a leak. If the new synthetic looks like pistachio pudding, that means it is milky and water is getting into the oil. New, it looked a clear dark green

Since it is coming out the prop area, you would then suspect the prop shaft seal OR the spool O ring. Actually, It doesn't much matter which it is since you must remove the spool to change either, so you may as well do both.

It is relatively simple: I'm a bit fuzzy (because the parts to my dual exhaust lower are in a very safe place in my garage) but I think there is a keeper ring to prevent the threaded ring from loosening, and a pin to keep the spool from rotating. SO, you unbend the tab or tabs on the keeper ring and unscrew the threaded ring holding in the spool. Then just pull the spool (don't lose the pin) and drive out the old seal. You may need to pull the prop shaft and reverse gear to remove the spool so then you will need to retrieve the shift yoke and re-install it upon assembly.

 

[mrwglo]

Re: Lower Unit Leak?

That is disappointing. I would have to say it had something to do with that hard freeze, everything looking so good up to that point. I'll search for a step-by-step on the forums here and if I don't find one I'll have to get a manual. That is essentially a Mercury lower, yes?

 

[Frank Acampora]

Re: Lower Unit Leak?

Yes, although it will bolt up to earlier Force engines and it looks like the earlier lower units, It has the Mercury water pump and gears. It also uses the mercury method of retaining the spool. Prop is different than earlier Force too. Essentially it is a Mercury lower disguised to look like a Force.

It IS a possibility that the freeze had something to do with the leak. You DID have the engine stored vertically so no water would collect in the case and freeze-crack it, --didn't you?

OOPS! Forgot! Because the filter is horizontal, an air bubble will form in it. Under sustained higher RPM running the fuel and air will vibrate and the bubble should work out. It will cause no harm because with or without the bubble, the engine will still be getting enough fuel. If it really bothers you aesthetically though, try relocating the filter.

 

[mrwglo]

Re: Lower Unit Leak?

I did have it stored vertically, but I had taken it out of the water just the day before the freeze. That shouldn't have been an issue though. I'm going to keep my fingers crossed and hope it was an unrelated and coincidental seal failure. I didn't notice any cracks anywhere and I did look, though I haven't torn it apart yet either.