Oil drain assembly question - trying to fix leak

I have a Fastrak w/ the Kawasaki 21hp engine that has an oil leak too big to ignore any longer. Everything seemed tight, so I'm looking to take off the oil drain assembly and look for a gasket to replace. It's not obvious to me how to best get the thing off though. The drain nipple coming off the side prevents me from getting a box-end wrench in there, and there's not enough clearance for the open end. I assume that the nut at the base of the engine is what needs to be turned and not the square section at the nipple since the nut at the base makes me think that's a union-like connection. The oil is all over the place, but the last time I cleaned it off and checked it out before it got that bad again, it looked to be coming from the oil drain area.

If I'm wrong about any of this, let me know. If you know the best way to go about this, I'd like to hear it.

(The oil is not coming from the filter. The mess there is from me turning it to get it off and it made a mess.)

First thing you need to do is give the unit a good washing and drying. Next you must figure out if the problem is the pan gasket, drain assembly or something else. After cleaning run the mower and carefully observe where the leak is.

From above:

The oil is all over the place, but the last time I cleaned it off and checked it out before it got that bad again, it looked to be coming from the oil drain area.

I've done that. Cleaned it thoroughly, checked right after the next mow and concluded that I needed to check the drain assembly. This mess is what I get after the 2nd mow after a cleaning.

EDIT:

Reading your response again, I should clean it and then run it without mowing to see the 1st signs. I'll do that.

That being said, I'd still like to know how to deal with removing this drain assembly in case it turns out my estimate is correct.

They make what's called a " Crow Foot " wrench, you can use that to remove the jamb nut that appears to be holding and securing the drain assembly, Look it up and figure out what size you need

Below the jam nut at the sump there is usually an oil-resistant O-ring that gets brittle with age and then leaks. The jam nut needs to be broken loose, then use a pipe wrench to remove the pipe extension.

This extension pipe may also be a 3/8 pipe thread into the sump and just require a good cleaning and then a good thick wrap with Teflon plumbers pipe sealer tape.

I see leakage above that drain pipe.

M20-2.5 fitting. Appears to be the Scag 482349 drain valve [Stens 125-734, Rotary 12112, Hustler 796524].

1" nut threaded M20-2.5 with a 15.8 x 2.4 o-ring

O-ring is Kawasaki 92055-0892 (Dash 114) JD M88478 and I do have a couple McMaster SKUs if needed.

Now the smaller o-ring I have never had a problem with so no data at hand as I am not opening a new package just to find out.

Hopefully this is not too much info.

As for oil leak oil does tends to flow downward so UV dye use might be needed to find the actual leak.

As star tech indicates the use of UV dye can make sure you are working on sealing in the correct place. You might get a surprise that the leak is not where you think. Hot oil leak can mislead very easily and I've seen oil not leak when cold.

Automotive stores usually has or can get UV dye KIT for about $20. Be sure you get the correct dye for motor oil. Run the engine for very short time and turn off and inspect in a dark place using the UV light and glasses. If you run it too long the dye might spread to other places. Do not over dose the motor oil, no need. You might need some dye for a final re-test or use later.
The dye stores really good.

No, Star Tech, not too much info for me at all. Top notch post - much appreciated. You all have been very helpful.

I'll need to check whether the dye I have is acceptable, but regardless, I need to order the UV flashlight. The kits come with glasses, but they list them as safety glasses. Are those needed for viewing the UV? If not, I can probably get a better quality UV light than that with a kit.

Here is a note on UV lights and UV dye. They must match in the nm range for brightest viewing. So verify the dye vs the LED light specs.

Here the UV dye I use is 365nm so I have a boosted 365nm focusable flash light. The light came with 1.5 AA but now I have 3.7v rechargeable in it as in my other led lights.

With the 365 nm extra strong light it is fairly visible in outdoor daylight. The UV dye I use is 374CS AutoPro from local auto parts house and from Amazon.