2011 LazerD kubota 25hp shuts down not overheating

I have a 2011 lazerD with the Kubota 25 hp diesel, about 1400 hrs. For the last few weeks it has started shutting down unexpectedly, at first it was after a couple hours of mowing and it was running a little hot. I tried replacing the thermostat, and changing the coolant, flow seems fine. That definitely helped keep the temp down, but still shutting down, now after only minutes of mowing. I have gone through unplugging temp sensors and oil pressure sensors one at a time to narrow down the problem, and I thought I had it narrowed down to the oil pressure switch as the mower ran great with that unhooked. After I hooked it back up though, the mower continued to run fine all day last Friday. Start my workday this Monday morning, and it shut down within 5 minutes of mowing, unhooked the oil pressure switch and it started to run just fine. Had to stop and shut down to talk to an employee, and now the mower won't run. Starts up and dies like it's overheated, but that isn't the case......I'm so lost at this point, any advice will help. I also know I have a hyd. pump for one of the wheels going bad, but I wouldn't think that would have any affect on the engine.

Check all wiring by hand at connections, switches, relays etc. making sure all is tight & secure, especially engine ground wires & straps from engine to chassis. Also make sure connections are rust & corrosion free. Make sue oil pressure switch is grounded.

mechanic mark said:

Replace water pump, impeller & bearing are shot.

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It's not overheating

mechanic mark said:

Check all wiring by hand at connections, switches, relays etc. making sure all is tight & secure, especially engine ground wires & straps from engine to chassis. Also make sure connections are rust & corrosion free. Make sue oil pressure switch is grounded.

Click to expand...

Yep, gone through all of that, can't seem to find any shorts, or breaks in any wiring, all connections look good, have cleaned all connection points, still can't figure it out. Contacted my ex-mark dealer to have them take it, and bring me a loaner. Very unimpressed with this set up from ex-mark, constant break downs, simple stuff usually, but if it takes 3 or 4 days for me to get a part I'm down for a week basically, and I've spent more time these last two summers working on my mowers than mowing. Horrible service from my ex-mark dealer too, takes forever for them to get back to me, they have forgot to send parts I've ordered before, and I have diagnosed and fixed problems that they couldn't figure out on their own.