How bad is it? Metal flakes in Lower Unit oil

[Moody Blue]

Did a pre-trip inspection today on my 1971 Merc 800 and all looked good until I drained the LU oil to inspect for water. Good new was that there was not a drop of water, BUT, the magnetic drain plug was covered in metal pieces. There was quite a bit of it. They were bigger than the normal "dust" like substance but smaller than chunks. I would describe them as "glitter like". I then took a strong magnet as swept it thru the drained oil and again it came out covered in metal bits.

So, my question is, do I run it until something gives or do I drop the LU and start the rebuild now? Obviously something is coming apart, but what and when will it fail?

Ran the motor all last weekend pulling skiers and tubing about 15 hours in total. No sign of trouble that I detected.

 

[Bifflefan]

Re: How bad is it? Metal flakes in Lower Unit oil

the real question is:

pay for it now? not real expencieve.
after it breaks, REAL expencieve.

it could last for ever or break the very next time.

 

[Moody Blue]

Re: How bad is it? Metal flakes in Lower Unit oil

Yeh I hear what you're saying. This is right in the middle of my vacation and I need to get a few more days running out of it. I have two spare units I could slap on at home but not until AFTER vacation.

Is there a "common" failure in these units? Bearing, gear, other? The debris is best described as tiny glitter like flakes.

If the LU does grenade, is there any possibility of causing damage to the powerhead?

 

[Bifflefan]

Re: How bad is it? Metal flakes in Lower Unit oil

if your on vacation id run it and just put it in the back of your mind. espcecially if youve got the parts at home.
Its like in racing, leading the race with 2 laps to go and the oil pressure is 0, run it to the flag and hope for the best.

 

[Moody Blue]

Re: How bad is it? Metal flakes in Lower Unit oil

Good analogy. The one thing I don't want to do is jeopardize the powerhead is something goes wrong in the LU. This is an old Merc 800 that is in immaculate condition and runs like a swiss watch. I don't have many spare parts for it and they are getting hard to find.

If the lower end goes it goes. Obviously something is coming apart and needs to be rebuilt. The piece(s) that are coming apart are no good anyways and there is so much metal contamination that all the bearings will need to be replaced as well.

I guess the big question is do I risk damaging the top end of the motor by running this as is? I never would have noticed something was wrong if I hadn't decided to inspect the oil. Damn my thoroughness !!!

 

[j_martin]

Re: How bad is it? Metal flakes in Lower Unit oil

I don't think it's real likely you'd hurt the power head. It is real likely you'll put parts out the side of the LU.

The flakes are likely metal from a seriously spalled bearing. If you're in the habit of chattering it into gear instead of smartly klunking it into gear, it could be from the clutch. That's not such a big deal if it's still working.
If it were a gear spalling, you'd been outa luck by now.

You might gain some time by using Mercury high performance Lube in it. If there isn't any available, use a heavy synthetic lube in it. Actually I'd run HP lube in it anyway.

On dirt track stock cars, you tape the gauges for the race so the driver doesn't get distracted. He's way too busy to be reading gauges.

The other thing to keep in mind is getting back to the dock. Murphey's law dictates that it will fail as far as possible from the landing.

hope it helps
John

 

[Moody Blue]

Re: How bad is it? Metal flakes in Lower Unit oil

Like I mentioned earlier, there was no sign of any problems. Motor ran strong all weekend. Only issue I had was that reverse would not reliably engage and would jump into and out of gear periodically.

I have since adjusted the shift cable for proper shifting.

I did put new LU oil in but am thinking that I'll drain that again and refill to try and flush out as much debris as possible.

 

[coolguy147]

Re: How bad is it? Metal flakes in Lower Unit oil

make sure ur idle isnt to high for the lu and shift brisk and quick probably clutch dog then

 

[j_martin]

Re: How bad is it? Metal flakes in Lower Unit oil

Like I mentioned earlier, there was no sign of any problems. Motor ran strong all weekend. Only issue I had was that reverse would not reliably engage and would jump into and out of gear periodically.

I have since adjusted the shift cable for proper shifting.

I did put new LU oil in but am thinking that I'll drain that again and refill to try and flush out as much debris as possible.

The debris is probably from the dog clutch skipping in reverse. Not unusual.

Most if no all of the metal stuck to the magnet. Any more loose in the LU will eventually get there.

I'd just go burn some fuel.

When you get home, plan on fixing the reverse clutch thingie before it sheds enough metal to totally fail.

John

 

[Moody Blue]

Re: How bad is it? Metal flakes in Lower Unit oil

Well I ran the motor for another 12 hours without any problem. The shift is well defined now as opposed to the vague reverse shift before I adjusted the cable.

Will be draining the LU oil tomorrow to see what comes out.