Help With Lower Unit Flush to Get Milk Out - What to use

WA-Newb

Petty Officer 1st Class
Joined
May 27, 2012
Messages
238
Fisrt Note...I am a total newbie to boats.

Today I am going to be doing a compression test on the motor I just got (had it started and running already) but would also like to start doing a flush on the lower unit to clean up the milky oil in order to see if the washers are causing the leak or something else. When I took the two screws off they were not very tight at all and I do not know how long the motor has been sitting exactly but it's been at least 3 years...most likely more.

This is a 1968 Starflite Selectric (Electric Shift), my uncle helped me start it, run it and shift through the gears until the thermostat opened before I agreed to buy it. The PO had spent a few hundred on this motor but ended up giving up and moving on to other projects.

Here is what I have in mind to try and clean out the milk / existing sludge and see if the washers are causing the problem.
I have a very very limited budget and it's usually coins that will fall out of my wallet if anything...lol

Step 1
Drain milky oil overnight (done)

Step 2.
Replace with new oil that is prefereably cheaper then the "type c" that this one requires.
Q: Can I use ATF, cheaper gear oil and something else the first couple fills and run it safely?
Note: Type C is over $10 per quart

Step 3.
Once cleaned out I will be adding new washers to the drain and vent plugs, filling the lower unit and running the motor in water to warm it up for the compression test.

Step 4.
After compression test I will check the lower unit for water intrusion again.
If there is water I will have to wait for help or the manual in order to pressure test / vacuum the lower unit.

Hopefully this is enough info for you all...I have read that ATF will work to flush this but I just really want to be sure for this Electric Shift motor as I would cry if I did an Uh-Oh that ruined my future fishing season...lol
I have also heard Seafoam can be used but that too is expensive so I need to know what I am doing is the correct method and not just literally pour money down the drain...lol.

water-gearcase.jpg
 

Chris1956

Supreme Mariner
Joined
Mar 25, 2004
Messages
28,102
Re: Help With Lower Unit Flush to Get Milk Out - What to use

Just drain it and refill with type C oil. No need to flush it out. No need to risk ruining one of the electrical components of the motor.
 

WA-Newb

Petty Officer 1st Class
Joined
May 27, 2012
Messages
238
Re: Help With Lower Unit Flush to Get Milk Out - What to use

If I just fill it and run it...wouldnt it just turn milky instantly?
I am hoping to get it clean so I can see if it stays clean after installing the new washers.

Also...if it isn't flushed and I just leave it as is will the remainnng milky goo hurt or impact the shifting components?
 

boobie

Supreme Mariner
Joined
Nov 5, 2009
Messages
20,826
Re: Help With Lower Unit Flush to Get Milk Out - What to use

I would use ATF on a maual shift but not that one. Fill it with type "C" and run it. After that check it and change if need be. The type "C" is a heck of alot cheaper than a g/c repair. You might also want to take it into a shop and have it pressure tested before filling it the first time.
 
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