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Water in lower unit

L

loosenut

Member
Pulled the drain plugs today to change the fluid in the lower unit. Came out very milky. Last summer i did have some discoloration, I put new seals for the drain plugs in, also changed the water pump. I changed the fluid after a couple trips after changing the impeller, just to make sure i put it back together correctly. No problems. Thought i had it fixed. Now this. :confused:

Did i do something wrong? Something new going on? It is on a '95 merc 25 hp, serial #og157655.
Thanks in advance for any input.
 
Your oil was most likely just aerated--it looks similar to oil with water in it.

Too bad you didn't save the old oil. If you let it sit in a clear glass container overnight, any water would appear at the bottom.

Jeff

PS: If you get it tested, concentrate on vacuum testing. Pressure testing does little good.
 
When it builds up pressure, and oil leaks out, there's plenty left to do the task required of it--even 25 % is plenty. If the seals leak under vacuum, however, water will enter as the LU cools down and wreck the gears and bearings.

Vacuum test it and, if it's tight, fill the unit with lube and go boating.

Jeff
 
Manuals say pressure test after repairs .---------------------On most motors with 25% of the oil in them, the upper thrust bearing on the driveshaft would come to a dynamic halt !----------Vacuum testing is best done before teardown, it sure finds seals that are not properly installed or cocked from water freezing in between them !
 
I'm not trying to start a fight! Just a diy'er trying to figure out what to do.I can get a seal kit for $78. I don't like to throw away money, would rather spend $78 and some time, then a rebuild/ new lower unit. Would it be advisable to refill the lower unit, make a trip, drain it, put the oil in jar and see if any water separates? Thank you.
 
Would it be advisable to refill the lower unit, make a trip, drain it, put the oil in jar and see if any water separates?
Click to expand...
I would before I tear into it. As stated, pressure test before dismantling it.
 
..."On most motors with 25% of the oil in them, the upper thrust bearing on the driveshaft would come to a dynamic halt "

Not really. At 5,000 rpms, oil is being flung all over the place. Besides, that particular LU design has a oil lifter deal about the driveshaft to circulate oil as it spins (that aluminum 'barber pole' deal).

..."No water will get into a properly sealed lower unit !!"

Correct.

Jeff
 
It sat for two days before i drained it. When i drained it what caught my attention was the discoloration, a tan or light brown color.
 
..."..what caught my attention was the discoloration, a tan or light brown color."

Absolutely typical and no indication of trouble. You may be okay.

Jeff
 
Drive shaft seal is the culprit. Due to the age (a 95) and the fact i plan on keeping it, i am going to replace all seals. Found a kit on this site from sierra marine for $44. Anything i need to know before tearing into it? Thank you.
 
I got a schematic from here. I replaced the water pump last summer. Do I need to do it again? Thank all of you for the input. Will post how it goes. Have most of it apart now. Having even more fun, when I pulled the locking pin for the shift shaft,I noticed fuel by the engine. Short of the story - the primer diaphragm has pin holes in it. Ordered both kits, one for the carb ( couldn't get just the primer diaphragm ) and one for the lower unit.
Boat, stands for "break out another thousand" !!! Short of the power head, it will be a new engine!
 
I got the lower unit back together and mounted. Before i start it up ( have to rebuild the carb first) are there any checks i can make? Ie: should the prop spin freely in neutral, should i put it in forward or reverse? if so what should it do? Do not want to fire up and tear something up. I did not see where the shift shaft was when i disassembled. My bad. kmcrwbr1: thank you for the seal puller/ slide hammer hint. Made life easy.
 
Success! Got it apart, replaced seals, got it back together. And it actually worked! ! Fired it up at home with the muffs, drained the fluid, no water. Took it to the lake, ran it. Drained the fluid the next day, not on purpose other stuff going on, no water. Rebuilt the carb, had to tweak the idle a little, all good now.
A big thank you to all who responded. A great site.
 
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