A little metal on lower unit drain magnet question

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I am not sure if having a little metal on the lower units oil drain plug is normal or not on a '84 90hp Mariner.

There is just a little bit there and the pieces are really small. I am the new owner of the PO's boat and the maintenance history is not there. The oil in the lower unit did look fairly clean (dark blue greenish looking) but if it was a fresh service then maybe this is a clue to a bigger problem or is this normal as part of the shifting process since there is no clutch as in a car.

The lower unit is currently off as I was replacing the water pump assembly and I was not sure if this was something the plus average back yard mechanic should check or will it require a lot of special Mercury tools?

Would a photo be helpful? I actually washed the drain screw in gas with the pieces on it so that it would be better to see. I just forgot to bring it in and photograph it tonight.

 

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Re: A little metal on lower unit drain magnet question

Ok, here is the photo and it also has a shot of the top drive bearing under the water pump which looks good. The propellor turns smoothly when I hand spin it.

 

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Re: A little metal on lower unit drain magnet question

As you can see the filings are so small. Also, is there normally some type of o-ring or washer to help seal the screws from the elements?

 

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Re: A little metal on lower unit drain magnet question

Is it possible that this metal came from the water pump housing? I did notice a bit of a lip in the bearing surface of the water pumps housing. I was always told to feel for a lip of wear there and realistically that means metal is being worn away and it has to go somewhere ... right? I have no idea what a boat mechanic would charge if I brought the unit in as it is and said to check it out. I prefer not to spend much more on the motor as I still have to fix the boat :facepalm:

 

[capslock118]

Re: A little metal on lower unit drain magnet question

I doubt it has anything to do with the water pump housing; that's in a separate section of the lower unit.

A "little" metal shaving is normal, but anymore is an indication that the lower unit should be inspected.

What a "little" means is something I don't know, a mechanic would though - I can't tell you if what you have is a little or not.

 

[carholme]

Re: A little metal on lower unit drain magnet question

Hard to tell from the photo if there is a lot of silvery looking material in the swarf but if there is, it certainly looks like a bearing race. The bearing you are describing as looking good, definitely does not look good.

Two choices:
You can flush the gearbox a few times, replenish the oil and run it to see how quickly the material builds up again but if it were mine, I would be pulling the guts out of it.

If it is just a bearing, you may still save the gearing, providing the bearing has not worn to the point where the gears are slightly moving against each other as opposed to correctly meshing. If that engine driveshaft bearing is wearing, it won't be long before the pinion gear wobbles enough to break something.

Bearings and shimming is cheap compared to a lower unit.

Here is a parts listing for a 1984 90hp:

http://www.crowleymarine.com/mercury-outboard/278.cfm

Look under both Gear Housing sections to see the makeup.

Hope yours is something simple and that none of the swarf is from the gears.

Gerry

 

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Re: A little metal on lower unit drain magnet question

It seems that I have a Cam-Shift I driveshaft WITHOUT a preload pin at the upper end. I don't mind attempting to take out the gear set but I am a little confused on what holds everything in on the unit.

According to a manual I was reading, they talk about holding the driveshaft in a large vise and using a block of wood on the lower unit to hit against to drive the lower unit away from the driveshaft.

How do you flush the lower unit? What type of liquid and can I do this correctly while the unit is off of the motor?

 

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Re: A little metal on lower unit drain magnet question

Your right capslock... last night when I laid my head on the pillow to sleep it hit me like a ton of bricks ... "the water impeller housing flushes the metal parts out in the water since its an enclosed area". Thanks for the quick answer.

 

[carholme]

Re: A little metal on lower unit drain magnet question

You can use varsol to flush the LU.

If you have a manual, what type is it? Don't rush ahead of yourself and start pounding with a hammer.

The guts are held in the LU by a cover nut, item 70 in this link:

http://www.crowleymarine.com/mercury-outboard/parts/278_23.cfm

Once that nut is removed, you can clamp the protected end of the prop shaft in a vice and tap the gear case off the bearing carrier, item 63.

Once the guts are out, you will have to remove the pinion gear, item 10, by removing nut, item 11 in this link:

http://www.crowleymarine.com/mercury-outboard/parts/278_22.cfm

Once the pinion gear is off the driveshaft, the shaft is ready to come out and if stuck, you can also clamp the top of the protected driveshaft splines in a vice and tap the LU off

Here is a link to a condensed version of the Clymer manual and if you read the section "Lower Unit" you should have some idea of what needs to be done. Let the page load for 30 seconds:

http://web.ebscohost.com/serrc/pdf?...86dc-d8b91f1fe2a0@sessionmgr104&vid=4&hid=108

Gerry

 

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Re: A little metal on lower unit drain magnet question

Gerry, thank you for the fine instructions. I really appreciate it. My manual is the one that is a download and approximately 672 pages. Even though it is one mentioned for free on the forum I paid about $5.00 for the download. I am not sure if it is a OEM type or not. The funny thing about my manual is that the author says things like "Advice", "Safety Words", "Very Special Good Words", "Stop and Observe", "Bad News" and "Plan Ahead". This book has a real human touch. A joy to read even if it is a repair manual. Sadly the photos are not as well scanned but I do my best with it.

Now a couple of "I am almost ready to open it up but... " questions:
1. Does cover nut item 70 require a special tool?
2. Tool suggestion for nut item 70?
3. Normal counter clockwise thread on nut item 70?
4. Is the nut, item 11, that holds the pinion gear on something that requires a special tool?
5. Is it reachable by ratchet or box wrench?
6. Will I be removing the Shift Shaft Assembly or its okay to leave it alone (I don't have the Merc tool for that one)?

Thanks for the Clymer manual. Your being a great help. I just got back from Wally World with my qt of QuickSilver Lower Unit oil and a pump to fill it from the bottom when all of this is done.

Funny thing ... when I got my Sierra Water Pump kit it came with a lot of extra O-Rings that are very large so I am hoping the kit has the replacement O-Rings for the gear set as well.

 

[carholme]

Re: A little metal on lower unit drain magnet question

1/2. There is a special tool for it but you can make your own or if you have a Merc shop handy, they may let you borrow one.

3. Normal threads, CCW to remove.

4. You can get in there with a box end wrench. I also have a cut down socket. Get the carrier out first and once you see the insides, you will have no problem figuring it out.

5. With my cut down socket, I use a power bar to break the torque.

6. There is no need to touch the shift shaft.

Those kits usually come with different sizes as they apply to a few different engines so you will have a few bits left over.

Gerry

 

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Re: A little metal on lower unit drain magnet question

Well, I could just shoot the lower if they were not soooo expensive. The darn prop will not come off. I took off the nut, sprayed some penetrator on the shaft, hung the lower unit by the prop (three blade) so it was a few inches off of the ground, put the brass prop nut back on and tried banging it out with a ball peened hammer (flat side) with no luck. Not a budge. The nut looks kinda funny now and I was able to get it off but now I am not sure which direction to go. I think I will leave it suspended tonight and spray some more PB Blaster on the threaded prop shaft hoping it will do something good. Otherwise, I am not sure if the next step is the torch on the inner rubber hub housing or what. I read that the prop can literally shoot off as the rubber expands from the heat. Darn those no maintenance PO's. If I ever get this engine running it is going to be washed and lubed constantly. I had to deal with the frozen steering shaft, bad trim tilt and a complete electronics, fuel pump, water pump, carbs rebuild and a few busted bolts. Help! Like I said, I got the prop nut off, the tab bending lock washer and now the props in the way from getting to the rest of it.

 

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Re: A little metal on lower unit drain magnet question

Well, I went by the local shade tree mechanic boat guy and we wailed away on my trim tilt units hydraulics and after that we went over to look at the lower unit. He said that a little metal like he saw wasn't so bad but since I did not know the history to flush it, fill it back up, run it and check it again. He said if the gears were lining up well he wouldn't mess with it. Also, my stuck propellor he said pretty much don't mess with it and don't take out the gear set because the bearing holder inside could possibly have the galvanic reaction happening with the bearings and other parts and if it is working now it may not if it gets opened. He also said to put a 10psi air pressure check when the water pump base is in and see if it holds for 10 minutes. Otherwise I could be losing it at the shifter, drive shaft or prop shaft seals. He is a busy "good ole boy" and he is very busy which says something about his reputation and to me the advice. So after I finish my trim tilt repair I am going to flush the lower unit a couple of times, assemble the water pump and take it by him for the a $10-$15 pressure check.