Flushing the lower unit of old oil?

[Texas Prowler]

My lower unit oil has seen better days and I'd like to flush all the old oil out. The manual states the use of omc premium, type c and dextron transmission fluid as the preferred oils of use. From my previous experience i know the use of trans fluid will clean oil sludge. What methods do you guys use to remove old oil in the lower unit?

 

[racerone]

The 1974 50 hp is NOT an electric shift lower unit.-------------Type -C is not the preferred lube.--------You can use OMC hy-vis or other outboard gear oils.

 

[Texas Prowler]

The outboard is a 73. Its manual with oil pump assist. What weight/ viscosity oil Should i use? 80/ 90?

 

[F_R]

Yes 80/90 outboard gear oil. History: In some bygone years, OMC only sold "Type C / Premium Blend" and said to use it in everything. Years go by, and they came out with Hi Vis and said Type C / Premium Blend was only required in electric shift models. Dextron was only approved for emergency use if you could not find Type C.
Little known history: One of those old OMC oils was discontinued because it had a whale oil additive in it. They had to quit making it when whale hunting was outlawed. I grabbed the last can for my own motors. Sorry, it's all gone now.

 

[Texas Prowler]

Thanks F_R !

 

[boobie]

I'd flush it out with the ATF Dextron 2 and then go to the oil it calls for.

 

[Texas Prowler]

That's what I've been thinking. I was hoping to get confirmation of that here. Thanks!

 

[jimmbo]

Yes 80/90 outboard gear oil. History: In some bygone years, OMC only sold "Type C / Premium Blend" and said to use it in everything. Years go by, and they came out with Hi Vis and said Type C / Premium Blend was only required in electric shift models. Dextron was only approved for emergency use if you could not find Type C.
Little known history: One of those old OMC oils was discontinued because it had a whale oil additive in it. They had to quit making it when whale hunting was outlawed. I grabbed the last can for my own motors. Sorry, it's all gone now.

F_R, what exactly constituted "emergency use"? From what I know about oils, ATF doesn't have any extreme pressure additives in it that gear oils have. Of course the gears in these motors aren't Hypoid gears so maybe they don't need it.

 

[F_R]

Well, y'see there is some sort of a law that says if a manufacturer specifies his own oil (or some sort of "special" oil) be used, he has to specify an acceptable substitute. If there is no acceptable substitute, he has to GIVE you the right stuff. So, the ATF is an "acceptable substitute", to satisfy the law. Beyond that, marketing takes over.

 

[racerone]

If you want a lively discussion just ask--" what oil is best "---Always results many posts.

 

[F_R]

No Title

Here is a sample of compliance with the "special oil" subject. This is my Ford owner's manual. They imply that you must use Ford Motorcraft Synthetic or semi-synthetic motor oil. But then drop down to the bottom of the page, and they say it is not mandatory--you can use any oil that meets the specifications. Yeah, now try to figure out what the specifications are!!

 

[Texas Prowler]

F_R thank you for your help with this. Knowledge is key I'd hate to mess something up.
Racer.... I'm not looking to start a what is a better oil thread. Just wanted to know how you guys go about flushing old oil out The lower unit. SMH......

 

[racerone]

The drain plug is at the bottom.-------Drain oil.--------leave motor out in the sun for say 3 days to drain completely.------Fill with the new oil.

 

[bob johnson]

was the question directed at the fluid needed to FLUSH the old oil out???????

as in the drain the old oil, then add an oil thinning product to "wash" the oil out residue out...and then remove.........so that you have as clean an empty LU as possible before you add NEW LU oil

bob

 

[Texas Prowler]

was the question directed at the fluid needed to FLUSH the old oil out???????

as in the drain the old oil, then add an oil thinning product to "wash" the oil out residue out...and then remove.........so that you have as clean an empty LU as possible before you add NEW LU oil

bob

Yes Thank you.

 

[Texas Prowler]

Got er filled with 80/90. Shifts great! can't wait till I got the lake with this outboard!