Gear hardness and grit in mercruisers

As mentioned in another thread, I managed to crunch a magnet, the tip from the lower gear case lube screw, in my drive. I think it blocked the shift assembly, so when I move the shaft it snapped the tip off.

I recovered some of it, but the rest seems in small pieces or otherwise unrecoverable.

I obviously have the option of paying a shop a few hundred $$ to open the lower unit up and clean it out.

So what I'm wondering is, how bad is it to have the shards in there? We're talking grit the size of coarse sand down to almost microscopic.

It's not metal, it's ceramic... I looked up the material, and it's typically a Rockwell C scale hardness of 59... which unfortunately is nearly has hard as most case hardened gears. Anyone know how hard mercruiser gears are?

I suspect what will happen is that if the magnet bits circulate (they may not, they're mostly stuck on the shift mechanism) and end up in the forward or reverse gears or on the bearing contact surfaces they'll get crushed into small bits... the ceramic is very brittle.

So I could end up with scratches and faster than normal wear in that area. It doesn't help that they're magnetic, so they will tend to stay where they touch steel. I suppose the gears would tend to sling lube toward the outer case, so they might clean their faces themselves.

Anyone have any thoughts on this? If you spilled a pencil eraser size amount of sand into the gear case, how long before it failed?

I'm kinda upset about this... I saved some cash by buying a used gear case, and now it looks like I may need a new one anyway....

Erik

PS: I did think of one more thing... putting a stronger magnet inside the gear case to try to attract more shards... I'll try that in a bit. and I'll be careful not to break it.

Re: Gear hardness and grit in mercruisers

If you spilled a pencil eraser size amount of sand into the gear case, how long before it failed?

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Very quickly. Answers closer than that depend on speed and time.

Re: Gear hardness and grit in mercruisers

Re: Gear hardness and grit in mercruisers

To make things more annoying, I replaced the seals on the upper tonight and failed to solve the leak problem I was having with the vacuum test. I guess the seal wasn't the problem.

Any idea what it would cost to have someone tear it down and clean it out? I'm guessing some parts would be destroyed in the process, requiring refitting of the gears, because it's an older drive....probably the lower hasn't been apart since it was at the factory.

I'd love to chuck it all and order a new unit from SEI, but I can't do that until spring Maybe I could roll the dice again on a used unit, this time a whole drive...

Erik

PS: I'm giving up for tonight. beer time.

Re: Gear hardness and grit in mercruisers

Are you actually fixing what was leaking, or just replacig seals and things in hopes of finding the leak.
Even worse, we have no clue what you are even working on.

Re: Gear hardness and grit in mercruisers

...and another thing about magnets. Don't ever pick up bearings(balls or rollers) with a magnet. That was a clear warning from the instructor that it would rearrange the molecules and leave the bearing 'less hard', and as they say in the book...'shorten the life of the part'.


You live anywhere around central California?

Re: Gear hardness and grit in mercruisers

jtybt said:

...and another thing about magnets. Don't ever pick up bearings(balls or rollers) with a magnet. That was a clear warning from the instructor that it would rearrange the molecules and leave the bearing 'less hard', and as they say in the book...'shorten the life of the part'.

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You're completely kidding right?

Re: Gear hardness and grit in mercruisers

Tim,
Do I look or sound like a joker?

Re: Gear hardness and grit in mercruisers

jtybt said:

Tim,
Do I look or sound like a joker?

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hard to respond without being a smart alec... I'll just say that somewhere along the line I think someone over extrapolated something they were told about the impact of magnetic fields on bearing surface tribology, hardness and wear. Picking up a bearing with a permanent magnet really won't have any effect on it's life or failure rate unless you scratch it get it dirty by doing so. definately not trying to be a smart alec, but you've been somewhat misled regarding that one particular issue...

Eric, sorry about your magnet troubles. sounds like the kind of thing I would do... I can't think of any way to deal with it except to dissasemble and clean everything or do another drive. Is your upper in good shape? you can buy just a lower from sei...

Re: Gear hardness and grit in mercruisers

...and another thing about magnets. Don't ever pick up bearings(balls or rollers) with a magnet. That was a clear warning from the instructor that it would rearrange the molecules and leave the bearing 'less hard', and as they say in the book...'shorten the life of the part'.

Click to expand...

Sounds a lot like a Volvo EFI instructor I had years ago. Every other comment was how the manual was wrong. Turns out, the manual was right, he was wrong and didn's show up as an instructor the next year.

I think you also had an instructor with some personal opinions that may not be based on fact.

Re: Gear hardness and grit in mercruisers

Don S said:

Are you actually fixing what was leaking, or just replacig seals and things in hopes of finding the leak.
Even worse, we have no clue what you are even working on.

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Gah, I can't believe I did that again. I could have sworn I included my drive info.... must have been the other post. It's an R drive, Mercruiser, attached to a GM 5.7 block, 1981 vintage. I recently blew the gears on my lower half, which I think was due to damage sustained in an accident a couple years back. I had changed the lube annually, there was no water in it or other signs of trouble, no lube in the bellows (just some grease from the ujoint). I thought the whole drive was tight until I bought this used lower half and tried to put it all together, then I discovered the vacuum leak at the input shaft.

I tried a vacuum test with one of those mity-vac pumps from harbor freight.. basically a hand pump with vacuum gauge, and I attached a fitting from a cheap lube fill pump. I checked that by plugging the fitting with my finger I can pump the gauge up.

The drive pumps to max 5 inches of Hg. on the drive (up to 22 on my finger) When I stop pumping it drains down. I can hear the air sucking in at the input shaft. The prop shaft is ok, as is the fitting for the pump (it's on the lower hole). The other lube screw had a problem with the gasket that I fixed. So today I bought an upper seal kit (spent some time trying to get magnet parts out of the lower first) then took out the input shaft and U joints and, being careful to keep 'em in the right order and position, I replaced the seal and O-ring (I had to take the seal out of the larger ring and put the new one in by pressing it carefully... just like mercruiser to make it extra complicated).

Result was that I hear a little slower leak, but it's still leaking in the same place. I did also check and clean the shaft and housing surfaces while I was at it. They're both smooth, although the input shaft where the ring-in-a-ring seal goes is only smooth right where the seal rides... nearby toward the U joint end it gets rougher and dirtier. I cleaned it up, but I figured as long as the seal surface was clean and not grooved I was ok.

About the only thing I can think to do at this point is to try to get the seal working by pulling it apart again and making sure the shaft and seal are mating correctly... basically hold the seal in my hand and put it on the shaft and see if all looks good.

But then I still have to get those magnet bits out... probably I'll have to buy a new lower from somewhere unless I can find someone to clean the one I have out for a cheap price.

Erik

Re: Gear hardness and grit in mercruisers

Probably tmi, but what the heck... There is some basis for the thought that exposure to magnetic fields can soften bearing surfaces... but in each of the reports where it was shown, the impact was less than 5% and was only seen when they were running bearings strong pulsed magnetic field. control experiments where the just pulsed the part and then compared the surface microhardness didn't show a statistically significant difference. There are conflicting reports on the same subject. from a practical standpoint, how long do you thing the needle bearings in an alternator would last if subjecting them to a magnetic field caused a problem. For anyone who wants to think about this in a lot more detail... a good place to start is "Effects of pulsed magnetic field on thrust bearing washer hardnes", J. Bockstedt, B. E. Klamecki, Wear 262 (2007) 1086-1096 and references contained therein. Hope this is helpful. respectfully submitted...

Re: Gear hardness and grit in mercruisers

I was taught marine repair in a class given by the chief mechanic of one of the Mercruiser sponsored tunnel boat teams. He was taught by a Mercruiser instructor. I can only relay what I was taught.

It's been over 15 years but my recollection was the magnet re-arranged the alignment of the molecules. This was specifically in reference to the roller bearings for the merc lower drive shaft that comes with just the outer race and can be dropped out of the case when removing the vertical shaft. I'm sure if you ever removed the shaft, you know what I'm talking about. Picking up the loose roller bearings with a magnet was a definite No No!


Oh, And this was not about bearings in a magnetic field. As you say starter, generators an alternators have to live in these environments. The instructor specifically said 'picking them up' with a magnet...so contact. Contact of any iron object by a magnet does magnetize and so re-aligns the molecules along a N/S axis.

Re: Gear hardness and grit in mercruisers

jtybt said:

I was taught marine repair in a class given by the chief mechanic of one of the Mercruiser sponsored tunnel boat teams. He was taught by a Mercruiser instructor. I can only relay what I was taught.

It's been over 15 years but my recollection was the magnet re-arranged the alignment of the molecules. This was specifically in reference to the roller bearings for the merc lower drive shaft that comes with just the outer race and can be dropped out of the case when removing the vertical shaft. I'm sure if you ever removed the shaft, you know what I'm talking about. Picking up the loose roller bearings with a magnet was a definite No No!

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I hear you... what's funny is that metal molecules do move around at room temperature, morphology, tribology, etc... all sorts of things can change. what's amazing to me is that while the magnetism deal in that kind of a situation turned out to be nothing / false alarm, if you freeze the crap out of the same metal in liquid nitrogen, it gets harder. no question that cryotreating strengthens and hardens bearing surfaces, etc... who'd have thunk it...


Sorry for the hijacking eric... I got no idea of any way to help with your deal. if it were me, i am sure i would wind up with another lower drive for future repair or parts in the garage attic...

How in the world do you get gearcase components clean of a nice grinding compound that is magnetic and will stick to the gears?

Re: Gear hardness and grit in mercruisers

Cryogenically treating most metals will strengthen them but won't turn any metal into the hardness and toughness of a forged piece. Forging align molecules. Heating and quenching hardens the forging. Tempering lowers the hardness but increases it's toughness.

The whole idea is setting the alignment of the molecules. Magnets rearrange/change them.

It could be there has been a change in how things are looked at now.

Re: Gear hardness and grit in mercruisers

This "magnet causing the molecules to move around" is pretty darn funny. Its not even April fools day!

Re: Gear hardness and grit in mercruisers

Come on bruce, you know that's how the fuel line magnets work . . . Jeez.

Re: Gear hardness and grit in mercruisers

I forgot about those! How about those magnets you put on your sore back?

Re: Gear hardness and grit in mercruisers

You mean to say you guys don't remember any Jr high school science classes?

Any magnet will partially magnetize any iron object it touches. It aligns the electrons and protons north and south. Do you know how your compass works?

Re: Gear hardness and grit in mercruisers

cringes....