the manual gauges read 0
There was absolutely nothing there. After the area that the sender screwed into drained, it wouldn't even pump any oil back in to the passage.
no oil pressure would trash that engine fast
That's one of the puzzels here. I thought with all the running and testing I've done there would at least be some noise from the lack of oil. The engine still starts and runs just like always, except there is no oil pressure.
I probably ran it 150' back to the garage, then 30' out into the drive, to chain it to the truck so I could tow it to the local garage, then 30' more to get into the shop, and I don't know how many times I restarted it during testing. (many times even at full throttle) Strange huh? The engine probably should have seized solid by now, but still sounds good. It's almost like the oil is going every where except to the passage where the sender screws in. I had put new oil and a filter on after it was in the shop a couple days in case it was ice. (no change) I forgot to check the new filter yesterday, to see if it filled with oil, although I doubt it, as it sits just above the sender. (I had filled it a little better then half way when I installed it)
The Yanmar engines are generally very reliable
I agree, this has been a great little tractor with almost no problems, the only other trouble we've had is the knuckle where the steering arm attaches to the front wheel, broke. The only thing I don't like about it is the hydraulics are real slow, especially in the cold. I was told that if I could find the right mechanic that has worked on these and willing to stick his neck out, there is a way to speed them up.
Maybe you could talk to a dealership mechanic
I thought about that. The local dealer is over 40 miles away and something like that should be done in person, not on the phone. The phone might be OK if I personally new them, but I've never done any service work there, only parts. I most likely will talk to them though before taking any drastic measures.
I'll probably bite the bullet and pay the $120 plus shipping and get a service manual if I don't hit on anything else soon.