Filings in Lower Unit oil

[nokiddin]

Hey all, lookin for some advice.

I have a 1985 merc 90 inline 6 outboard. Last fall, while winterizing, I drained the lower unit and found some filings in the oil. There were quite a few stuck to the drain screw and in the oil. The oil didn't seem to have signs of water intrusion.

I'm assuming the filings are an indication for me to investigate further. Could you guys provide me with tips on what my next steps are?

Last season was my first season with this boat, so I don't know much about what happened to it before that. Last summer, it seemed to shift fine, but would clunk a bit if you kinda hovered just out of neutral and didn't push the control far enough forward (hard to explain) but I assume that this would happen on any engine.

Thanks for the help!

 

[JB]

Re: Filings in Lower Unit oil

Some fine filings are going to happen. That is why you have a magnetized plug, and it is also why most of us renew the lower end lube annually.

 

[Bondo]

Re: Filings in Lower Unit oil

Hey all, lookin for some advice.

I have a 1985 merc 90 inline 6 outboard. Last fall, while winterizing, I drained the lower unit and found some filings in the oil. There were quite a few stuck to the drain screw and in the oil. The oil didn't seem to have signs of water intrusion.

I'm assuming the filings are an indication for me to investigate further. Could you guys provide me with tips on what my next steps are?

Last season was my first season with this boat, so I don't know much about what happened to it before that. Last summer, it seemed to shift fine, but would clunk a bit if you kinda hovered just out of neutral and didn't push the control far enough forward (hard to explain) but I assume that this would happen on any engine.

Thanks for the help!

Ayuh,... Either Don't do that, or adjust the cable so it don't do it,...
These motors need to be shifted Briskly...

That's probably where the metal came from...

 

[Mi duckdown]

Re: Filings in Lower Unit oil

^ what bond-o posted

 

[Moody Blue]

Re: Filings in Lower Unit oil

I drained the lower unit and found some filings in the oil. There were quite a few stuck to the drain screw and in the oil. The oil didn't seem to have signs of water intrusion.

All depends on the kind of filings. It it appears as a fine metal "dust" like material, then that is normal as stated above. If the metal is slivers or small "chunks" of metal then you have a problem. Generally if you can't feel the grit when you rub it between your finger and thumb then everything is OK.

A slow or uncertain shift results in the clutch dog slipping/grating over the gear dogs resulting in excessive wear on both the clutch dog and gear resulting in the metal you are finding. A quick and deliberate shift is the best practice.

 

[nokiddin]

Re: Filings in Lower Unit oil

I'd say the filings were like small slivers, that I could just feel, definitely not chunks.

Now that I have learned how to drive this boat (first time with a boat), I won't be grinding things anymore hopefully.

Is the best bet to fill it with oil, use it, and then at the end of the season check for more filings?

Or should I be doing something more proactive, prior to the season?

 

[Moody Blue]

Re: Filings in Lower Unit oil

Is the best bet to fill it with oil, use it, and then at the end of the season check for more filings?

Or should I be doing something more proactive, prior to the season?

That would be my approach. Drain the existing oil completely and refill with the proper lower unit lube. Run the motor for a period of time and pull the drain plug for inspection. If the metal debris is again present or getting worse then further investigation would be required. Taking the lower unit apart is not a simple task.

You didn't indicate how often the oil was changed prior to your service last fall.

Make sure that the shift cable is properly adjusted so that you can shift gears properly with minimal grinding of the gears. A poorly adjusted shift cable and worn shift cam on my motor destroyed my clutch dog and reverse gear requiring a rebuild of the lower unit.

 

[nokiddin]

Re: Filings in Lower Unit oil

I am not sure how often the oil was changed prior to the change I did last fall, as I bought boat last summer. If i remember correctly, the oil had been recently changed before I bought it, however I am not positive. The guy I purchased from seemed to be the kinda guy who did a lot of maintenance of his machines, but who knows.

Any pointers on the process of ensuring the shift cable is adjusted right?

 

[mercurymang]

Re: Filings in Lower Unit oil

Also, from what i understand, if you idle speed is too high (nearing 1000 rpm) it is hard on your LU when shifting bewteen positions. Any idea what your idle speed is?

 

[nokiddin]

Re: Filings in Lower Unit oil

Can't remember the idle speed. But I'll check that out when I fire it up in a month or two.

 

[nokiddin]

Re: Filings in Lower Unit oil

Sorry for the delay in posting in this thread, but I want to change the impeller. So, since I wanna drop the LU anyway to change the impeller, should I go a little further and check out the gears for problems? I've never done this before, so I don't know how much extra work it would be to do that.

 

[Moody Blue]

Re: Filings in Lower Unit oil

Unless there is some obvious reason to do so, I would avoid opening up the lower unit.

Was there any sign of water when you drained the oil? If not, then I would leave it alone.

Does it shift properly into FWD/N/REV ? If so, then I would leave it alone.

If it aint broke, don't fix it.

 

[tazrig]

Re: Filings in Lower Unit oil

Sorry for the delay in posting in this thread, but I want to change the impeller. So, since I wanna drop the LU anyway to change the impeller, should I go a little further and check out the gears for problems? I've never done this before, so I don't know how much extra work it would be to do that.

It is very important to change out the impeller every other year regardless of how much you use the engine. Your gear fluid should be changed out annually (and or every 50 hours) at the end of the season as part of your winterization. I just want to make sure you understand how things come apart on your motor. Dropping the lower unit to replace the water impeller is an easy job and even after you remove it from the rest of the engine the "gear case" is still fully intact. They are 2 different things. Messing with the gears and clutch is a major job. Especially for the uninitiated. As others have stated, going forward, shift quickly so there is no grinding. If you can do this your cable is fine and doesn't need adjusting or replacing. If your engine can only rev up before it shifts then you need to re-visit the cable issue. If you want to be on the safe side run the motor for say 10-15 hours and change out the oil again to look for more or worsening and enlarged shavings.

 

[tazrig]

Re: Filings in Lower Unit oil

If it aint broke, don't fix it.

^^^+1 Big Time!!

 

[nokiddin]

Re: Filings in Lower Unit oil

Hey guys, thanks for the replies. I do understand that changing the impeller is a different job than opening the gearcase. And i have a shop manual for the engine. I will leave the gearcase alone as the shifting and motor are working fine