# Mercury lower unit seals shot



## bulafisherman (Apr 11, 2004)

I have a mid 85s mercury 25 XD, a few weeks ago i took it out for the first time, when I went to tilt it back after getting out of the water to attach the transom, oil ran out of the weep hole, a few days later I went to drain the lower unit oil and pretty much had nothing but water in my lower unit, I am waiting on a seal kit to tear it apart and replace the seals and o rings, what are the odds of having damage that will require more than replacing the seal or seals that failed? IAM not sure what to expect, I have replaced impellers but never gotten into more of the lower unit details than that.


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## KaGee (Sep 8, 2006)

You may have bad seals, who knows. The failure to replace the washer/seal on the fill/drain screws every time they are removed cause more water intrusion than anything else. A lower unit should be pressure tested prior to purchasing parts.


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## cincinnati (May 24, 2004)

Have had seals replaced several times in my ‘88 Merc 25 HP. Gear lube has shown from heavy ribbon of emulsion to, worst case, heavily creamed coffee.

Do my own impellers, but send the seal job out: think there are 4 seals - 2 propshaft & 2 driveshaft - which is too many for me until I’ve seen it done. 

Shop usually charges 1 hour, plus materials & tests pressure AND vacuum. Last trip, the unit passed pressure but failed vacuum. Propshaft was slightly worn & was replaced.


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## Harry1959 (Mar 17, 2011)

It may not have hurt anything. Hopefully you didn’t see metal shavings in the water you drained out. Couple years ago I unknowingly put my drain plug back in without the little washer. Realized it when I attempted to drain it for fall storage, I had ran it empty for several short fishing trips. I’d say I got lucky, no metal shavings and have used the 2003 25 hp merc 2 cycle many hours since then. No issues yet...... I don’t recommend you try this at home. Lol


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## firemanmike2127 (Mar 17, 2013)

To answer your question. It's POSSIBLE that the bearing surfaces or gear teeth could be moisture damaged. If not much time has lapsed you might have dodged the bullet. Sometimes the bearing surfaces & gear teath only have minor rust 'staining' that hasn't etched into the hardened surfaces. If it only had water in it for a day or two there PROBABLY isn't any significant damage. Pulling the prop shaft bearing carrier will allow you to inspect the pinion gear teeth. The prop shaft might be all stainless or a friction welded component that could have been affected (on the internal portion) by the recent water intrusion.


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## bustedrod (May 13, 2015)

I have an 86 90hp merc that I just replaced the fill screw gaskets, very well known to leak. and the shift seal bushing. and the water pump . then pressure chkd ok. I dought if its hurt, these things are built like tanks .


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## sherman51 (Apr 12, 2011)

i am one of the guys that believes everything shout be ok. I've had the same thing happen a couple of times over the yrs ive been boating.
sherman


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## bulafisherman (Apr 11, 2004)

Thanks for the replies guys, iam waiting on the seal kit and a repair manual that I put on hold at the local library, I have a friend that went to school for his marine mechanic certification some years ago, he doesn't work on them much anymore but is knowledgeable and is going to help me do the repair, we will pressure and vacuum test it.


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## bountyhunter (Apr 28, 2004)

DO A U TUBE and watch it a couple times.


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## firemanmike2127 (Mar 17, 2013)

I'd recommend soaking the bearing carrier & it's spanner retaining nut with some penetrant ahead of time...especially if this gearcase is from an older motor. They can be challenging to remove (intact) if there's some corrosion present or the last person that had it apart didn't properly coat the metal to metal surfaces with an appropriate sealant. Mike


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## bustedrod (May 13, 2015)

it sounds like your well on your way to fixin that L U ... a lower unit isn't as scary as ya think . good luck as soon as ya pressure check your leaks will show.


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## fastwater (Apr 1, 2014)

firemanmike2127 said:


> I'd recommend soaking the bearing carrier & it's spanner retaining nut with some penetrant ahead of time...especially if this gearcase is from an older motor. They can be challenging to remove (intact) if there's some corrosion present or the last person that had it apart didn't properly coat the metal to metal surfaces with an appropriate sealant. Mike


Amen on soaking the bearing carrier and nut in penetrating oil.
I had one several years ago that I tried spraying down and letting soak for two to three days. Still couldn't get carrier out. Ended up putting about two gal. of automatic transmission fluid in a bucket and dropped the lower unit down into it. Let it soak for about a week tapping gently periodically with a rubber mallet around the housing. Carrier finally came out.

Forgot to add...careful what kind of penetrating oil you use. Don't use PB Blaster. There's an oring in a groove around the outside of the carrier that helps seal out water. If the oring soaks in Blaster very long, the Blaster will swell the oring making the carrier even more difficult to remove.
Have had success using Liquid Wrench penetrating fluid without affect to the oring. Again, transmission fluid works great as well


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## bulafisherman (Apr 11, 2004)

Thanks for the tips firemanmike and fastwater, good to know.


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## firemanmike2127 (Mar 17, 2013)

No problem. The best product to use for the white corrosion typically found on bearing carriers & the spanner not is Oil of Wintergreen. This stuff smells like spearmint gum & is the consistency of water. The proper chemical name is Methyl Salicylate. I got this tip from a Mercury Marine Service School instructor back about 1980. I ordered it from my local drug store & keep some drawn up in a hobby syringe with a thin curved dispensing tip. It's earned it's place on my workbench many times over. The other tip that can be found in the older factory service manuals is to heat the area where the spanner nut threads are. Mercury Marine used to sell a high powered little heat lamp just for this purpose. The manual instructions were to 'apply heat to the gearcase around the threads until the paint blistered'. Mike


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## bulafisherman (Apr 11, 2004)

In the process of taking apart the lower unit this weekend, discovered IAM in need of a prop shaft, wear around the shaft where the bearing carrier oil seal is, New one is 350, haven't run across a used one on eBay, wondering if it could be taken to a machine shop, the worn groove Tig welded than machined down, looking for options now. Need to get back on the water.


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## cincinnati (May 24, 2004)

A machinist friend likes to tell people, “Anything can be repaired. How much do you want to spend?”

Unless you have a machinist friend, you should price that machine work, before you rule out the new propshaft.

350 for the part seems a little higher than what I remember, but maybe the shop gave me a break since they did the work....


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## fastwater (Apr 1, 2014)

Like Cinn. said, it can be welded and machined. But price it out first. Sending you a PM with contact info of an OGF member in the machining business.


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## Saugeye Tom (Oct 6, 2010)

fastwater said:


> Like Cinn. said, it can be welded and machined. But price it out first. Sending you a PM with contact info of an OGF member in the matching business.


tHAT WOULD BE MI sEND THE PICS TO MY CELL AND i CAN GIVE YA A QUOTE


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## Shortdrift (Apr 5, 2004)

Lots of used Merc parts available on the Internet. Search 'old Mercury Outboard Parts"


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## ya13ya03 (Sep 21, 2010)

I'm a machinist by trade and I've tried to do this a few times. Usually the welding will distort the shaft and it won't run perfectly true after machining. That shaft needs to run perfectly true or it'll waste the next seals in short time.


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## firemanmike2127 (Mar 17, 2013)

Since a new prop shaft is $ 350.00 I'd consider looking for a complete gearcase. If you ever shell a gear set you'll already have spare parts left over from this repair. You might consider looking @ Speedy Sleeve's website also to see if they offer a stainless steel sleeve of the correct dimension to fit your prop shaft seals. You'll need measure the diameter of your prop shaft where the seals ride (the non-worn area) to have a dimension for comparison. If they have one that's the correct size you'll be able to simply turn down the prop shaft down enough to epoxy a sleeve into place. That would be the least expensive alternative. Mike


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## bustedrod (May 13, 2015)

the sleeve is a good idea but it can be heated slightly and put on , also another way is have it hard chromed and ground . was a machinist for 40 yrs and there are many ways to fix it but money deems the type of fix.


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## firemanmike2127 (Mar 17, 2013)

Usually the O.D of the prop shaft is the same where the carrier bearing rides & also the portion where the prop shaft seals sit. This is a mid 80's engine so I would certainly think the most economical alternative is in order. Hard chroming is an option I've used before. If he's even able to use a sleeve it will have to be existing diameter of the shaft where the seal rides IMO.....otherwise the bearing carrier won't slide back over the prop shaft. Mike


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