help water in lower unit

L

lt210

Cadet
Joined
Mar 24, 2004
Messages
22
i have a 1964 merc.500 50 hp that i just traded for and i was checking it over and i was changing the oil in the lower unit and whene i draind the oil nothing came out but clean water not to much oil came out.i had it sitting in a barrel of water for about a week tunning and it runs great ,but i suspest that i need to replace the lower unit seals is this somthing i can do ore does it take speceal tools .i i am a mechaic for a fire department not to much boat motor exper.serial number is 1677271 and the out put shaft brings seam to be ok not lose can some one help thanks jason.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: help water in lower unit

Hi, Jason.<br /><br />The most common cause of water in the gearcase is bad gaskets under the fill/vent screws. They should be replaced on EVERY gearcase oil change.<br /><br />You may have a leaky seal. A shop can pressure test the gearcase for you to diagnose the seals.<br /><br />Good luck. :)
 
Chinewalker

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: help water in lower unit

Hi Jason,<br /> Judging by the vintage of your motor, simply replacing the seals likely WON'T solve your problem. Just about every one of those I've seen with water intrusion problems can be traced to corrosion on the driveshaft in the area of the upper seal (under the waterpump cartridge). Those mild steel shafts are prone to rusting, particularly in that area as water can puddle there.<br /> I would pull the unit off, and remove the water pump cartridge to inspect the condition of the shaft. If the shaft is pitted, you can do one of several things. You can have the shaft welded and reground. You can install a SpeediSleeve. You can fill the pits with JB Weld and smooth it out. I've done the third fix on a few of my motors and it seems to work alright so far, but I'm not sure about the permanence of the fix. All three require complete disassembly of the unit. Start with the inspection and go from there...<br />- Scott
 
L

lt210

Cadet
Joined
Mar 24, 2004
Messages
22
Re: help water in lower unit

thanks for info and i sent you a email i think
 
M

Mercury140-I6

Petty Officer 1st Class
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Nov 6, 2003
Messages
339
Re: help water in lower unit

Ok, I'm a little confused about this gasket on the fill and vent screws. My parents had a 1969 1250 that I know didn't have any kind of gasket on either the vent or fill screws and it never leaked water till 1993 when one of the reed valves took out #5 piston. I have had a 1979 Mercury 140 for the last 8 years and I am pretty sure that it doesn't have them either and I change the lower unit fluid everyother year if not every year and have never had water in the gearcase. I am almost afraid to put them on now ;) . Where can I get them and can they be missed when changing the fluid that many times?<br /><br />Craig
 
A

andrewkafp

Lieutenant Commander
Joined
Mar 15, 2003
Messages
1,668
Re: help water in lower unit

A 1979 Merc DOES have 'em.. But they can either come out and roll away when you remove the screw or "Hide" in the recess around the hole. If yours hasn't leaked, it is most likely that you have been lucky enough to have a good flat surface between the screw head and the Alloy L/U. I recently replaced mine with bright blue ones so they are easier to see when I put the screws back in. They are usually clear or black plastic.<br /><br />Part no 12-20260 WASHER<br />12 - 19183 2 for the Jet motor
 
C

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,467
Re: help water in lower unit

Let me chime in on the usefullness of fill/drain screw gaskets. I started to use them recently to protect the fill/drain screw threads from corrosion. I have never had a leak of water into the gearcase through the fill/drain screw openings without gaskets. It is just that the saltwater corrosion makes the screws difficult to remove.
 
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