Turns out the connecting rod bearing at the crank was seized. I put some oil on it and after a little rocking it came free but the damage is done, it feels gritty and makes a terrible noise even just moving by hand.
So Sunday night after visiting my wife's uncle for his birthday we stopped at Harbor Freight:
Yes another Harbor Freight compressor. Normally I don't buy Harbor Freight tools with more than 1 moving part but since the first one lasted so well I figured I was safe to go again. This one is a 2.5hp, 21 gallon unit that cost $100 more than the first one but its a way better compressor and weighs about 3x as much.
Sadly I'm going to have to get some electrical work done in my garage, 2.5 HP is 1875w (1hp is 750w) which is 20a which is all the power I have in my garage. Using the long extension cord I've always used the compressor won't start. At first I thought it was because its cold out so I brought it in the house and let it warm up. Inside and warmed it ran fine (although its very loud) so I took it out again where it again failed. Then I had inspiration and put it on a short extension cord (the outlet is blocked by a snowmobile) and it ran. With only one outlet in the garage this is a problem. Realistically I'd like to have 220v in the garage and existing wiring is also just barely adequate for my welder so I need some more power out there.
I'd like to have 220v run to a sub panel with a couple 20a circuits so I could run the compressor, welder and some lights at the same time. Someday I'd like to have a 220v welder and compressor but if I'm dreaming I guess I'd start with a pony...