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water in lower unit 1996 125 hp

H

hot fudge

New member
I have twin 1996 125 hp Mariner outboards. Recently while changing the lower unit oil , I noticed some water in the mix (3-4 oz). I realize that this is not good and that I probably have a leak somewhere. Should I change the water pumps with a water pump kit (18-3265) and buy a lower unit seal kit (18-2626) for each engine. Is there anything else it could be that is causing the leaks or that I have to worry about? Are those the correct part numbers? thanks
 
Re: water in lower unit

I would start by taking the motor(s) to a dealer and having a lower unit pressure test done - you don't want to start tearing them down and replacing seals if it is simply a missing seal on the fill or vent plug (for example) - the test plus a couple new washers might be 50 bucks - a lower unit reseal could be many hundreds of dollars.

If the waterpump impellers are more than 2 years old, they should be changed. And if you don't know or can't remember "how old" then I would install complete kits.

You have cited some Sierra part numbers there so I can't say if they are correct or not - for water pumps, seals and gaskets I stick with OEM unless they are absolutely not available - they are only a little more expensive than aftermarket, and I have found them to be significantly superior in quality.

I do use the aftermarket parts for ignition systems however, and consider them to be as good as or better than OEM in some instances...
 
Re: water in lower unit

ok thanks. I might try that. I will probably end up changing the water pumps. Do you know If I need to buy a lower unit seal kit along with the water pump kit. or can I change teh water pump w/o opening upthe lower unit?
 
Re: water in lower unit

If you know water is getting in to the unit what will the test tell him (us)? Can it pinpoint the leak? Thanks i have the same pro.
 
Re: water in lower unit

Yes, a properly done pressure test will tell you "where" the leak is.

The four main sources for water intrusion into the lower unit would be (in no particular order):

the seals on the fill/vent/level plugs/screws (many models only have fill and vent plugs)

the big o-ring (seal) on the bearing carrier

the propshaft seal

the waterpump base/seal

A proper test would involve applying air pressure to the lower unit (normally pumped in through the oil fill with a pressure gauge connected to the oil vent). The propshaft, driveshaft and shift shaft are then rotated or wiggled and if the air pressure drops then you move onto the next step.

The unit is then submerged in water, where you can see where air is escaping - thus determining which seal has failed.

Many shops will charge about 1/2 hours labour to do the test. If you have a compressor (need 10-15 psi in the lower unit) and a pressure gauge you could do it yourself at home....
 
Re: water in lower unit

WoW This is great info, i,ve got all the seals. I,m was just hopeing it,s on the top side, before i make the special tools for the lower. I know this motor was salt run.
 
Re: water in lower unit

Great info! I've got a simple question - where is the big o-ring (seal) on the bearing carrier? I've been going over schematics, looking for the bearing carrier and can't find where in the lower unit it resides.



galamb said:
Yes, a properly done pressure test will tell you "where" the leak is.

The four main sources for water intrusion into the lower unit would be (in no particular order):

the seals on the fill/vent/level plugs/screws (many models only have fill and vent plugs)

the big o-ring (seal) on the bearing carrier

the propshaft seal

the waterpump base/seal

A proper test would involve applying air pressure to the lower unit (normally pumped in through the oil fill with a pressure gauge connected to the oil vent). The propshaft, driveshaft and shift shaft are then rotated or wiggled and if the air pressure drops then you move onto the next step.

The unit is then submerged in water, where you can see where air is escaping - thus determining which seal has failed.

Many shops will charge about 1/2 hours labour to do the test. If you have a compressor (need 10-15 psi in the lower unit) and a pressure gauge you could do it yourself at home....
Click to expand...
 
Re: water in lower unit

Here, check this out - #54 is the bearing carrier and #55 is the O-ring...
 
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Re: water in lower unit

95 is 2-4-C with Teflon (which is a Merc product - any multi-purpose lube with teflon will do), 94 is anti-seize, 87 is regular high speed bearing grease and 7 is Loctite (red)
 
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