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This has happened repeatedly.
The mower has 308 hrs, purchased new in 2022—home use. Stored in a dry shed.
I have checked all the wiring I can, loosened, examined, and retightened the ground on the engine. I tried, but without success, to pull apart the electrical clutch connection to check the clutch. I am wondering if perhaps that connection is corroded and dirty, and that could be a factor. The delay in blowing the fuse means something.
Thank you in advance for your suggestions!

Are you releasing the locking tab on the connector housing? And sometime it does requires pliers to get connection apart.

StarTech said:

Are you releasing the locking tab on the connector housing? And sometime it does requires pliers to get connection apart.

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Thanks! I slipped a small screwdriver under the locking tab, pushed it down and then pulled with a small vise grip on the short end and water pump pliers on the long one. It moved about 1/16", then the pliers slipped. It is hard to tell how tightly to squeeze without crushing the connector housing. The small screwdriver did slip out, too. Will give it another go.

Does this only have the single 20A fuse? Has there been jump started going on? 308 hours on a PTO clutch is nothing for one of these machines.

I would suspect a rub through in the harness somewhere.

Usually, I install a 20A automotive circuit breaker while I chase these kinds of problems down.

Auto Doc's said:

Does this only have the single 20A fuse? Has there been jump started going on? 308 hours on a PTO clutch is nothing for one of these machines.

I would suspect a rub through in the harness somewhere.

Usually, I install a 20A automotive circuit breaker while I chase these kinds of problems down.

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Thanks! Yes, it has a single 20A fuse mounted on the tiger eye console between the seat and the console. That circuit breaker will be a great time saver.
I was surprised to encounter this problem with so few hours on the machine. With a new fuse, it restarts right away, even when hot. I have not yet tried to mow again immediately. Will do that.
Looking at the wiring again today

The electrical connector to the clutch was successfully pulled apart after running a small screwdriver around the inside perimeter of the connector to loosen it.
The multimeter on 2000 ohms shows 000. I suppose that means the clutch needs to be replaced. Or am I missing something? Not an expert on this, I thought there would be SOME reading above 000.

Did you touch the meter lead tips together and verify the meter and leads are actually good? Usually, the leads will read .001 or .002 resistance on average.

If the meter checks out good, then I would next suspect an open in the wiring to the PTO clutch. Rodents love wire insulation.

Typically, a burnt PTO clutch winding will read very high resistance.

Thank you!

I touched the tips, and the reading wound down to 000 after starting at .004 ish.

The factory wiring I can see appears to have no apparent damage. We do have crazy mice here.

The clutch does work at first. The machine mows for 20 to 30 minutes. Then something causes the 20-amp fuse to blow. New fuse, mower works fine, but for less time. Second fuse, even less time.

The pigtail connecting the clutch to the machine shows no apparent damage.

I recommend you check all of the rest of the wiring carefully because it is very unusual for a PTO clutch to fail this soon. Commercial units use similar PTO clutches until you get into the 72-inch cut or wider.

A simple test you can do is disconnect the PTO clutch from the main harness and make a short harness with connector pins you can connect to the PTO clutch lead. Install a fuse holder with a 20A fuse in one of the wires. Then connect it to a battery and see how long it holds the clutch closed. The PTO clutch windings do not have a particular polarity when it comes to connecting battery.

Monitor the leads for getting hot. Warm is okay, but hot is not good. If it blows the fuse after about 20-30 minutes, then that would confirm the clutch windings are bad.

Auto Doc's said:

Did you touch the meter lead tips together and verify the meter and leads are actually good? Usually, the leads will read .001 or .002 resistance on average.

If the meter checks out good, then I would next suspect an open in the wiring to the PTO clutch. Rodents love wire insulation.

Typically, a burnt PTO clutch winding will read very high resistance.

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You really need learn electrical diagnostics.

Low ohms reading below 1.7 ohms usually indicates either a partial or a fully short PTO clutch winding. BTW an open circuit would read 1999 on most Ohms meters. Normal resistance is between 1.7 to 3.5 ohms depending on the clutch.

And a burnt PTO clutch winding will read a shorted condition and not a high reading as the winding enamel coating be burned off allowing the windings to short circuit themselves. Also if the clutch mechanically fails it can damage the windings creating a direct short to ground.

An alternate way to tell if PTO is a having shorting condition is to install a 7 amp fuse inline with the clutch. IF the fuse blows then the clutch is shorting out.

Auto Doc's said:

Install a fuse holder with a 20A fuse in one of the wires.

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I have PTOs to as much 20 amps and still work.

Auto Doc's said:

The PTO clutch windings do not have a particular polarity when it comes to connecting battery.

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Provided the clutch or permanently attached lead does not have an internal diode.

Is this what you mean?