Yamaha 200 HPDI - gradual power loss before cut off

[hunt15]

I am hoping that someone can help me diagnose this problem.
My son was running the boat, 22' Grady with a 200 HPDI.
He says that he hit a wave and then after that he could only go about 7 MPH, instead of the 28 that he was cruising. He called on a cell phone, I asked him to rev in neutral (which it did just fine), thought it might be fishing line around the prop (he couldn't see any.)
Towboat US wasn't available for about 3 hours so I asked him to head the 5 miles home. Gradually lost speed (calls at 3 MPH and then 1 MPH and finally engine cut out.)

Got it towed home, pulled the prop, no line and the prop seems fine. Engine won't start. Cranks fine, engine oil OK.
Any suggestions on were to start looking. The gradual power loss has me stumpted.
Thanks

[hunt15]

forgot to mention. Nut holding prop on was loose. Two unrelated issues here??

[jb123]

prop nuts usually dont unloosen unless installed with no pin or locknut, from first glance id say a spun hub on prop.look at both sides of prop to see if you see any rubber out of place.

[hunt15]

Thanks JB. It was a spun hub. New prop and plugs and it runs great again.