Troy Built (Year 2012) Briggs and Stratton 6.5 horse Pressure Washer

I have a Troy Built pressure washer with a Briggs and Stratton motor that I've had for a few years.  Yesterday I used it for the first time since last season, changed the oil in it, put fresh gas in, and made sure the air filter was good.  It ran well for about an hour or so and then it suddenly got much louder, like the motor was working harder than normal, and then it shut off. 
 
Now it only runs for a few seconds after pull start before shutting off.  I tried changing the spark plug but that didn't fix.  I don't think the pump is locked up because it does build a little pressure for the short time that it's running.  At a loss for what it may be.  Is the motor just wore out?

SRTsFZ6
You have to narrow down if it's the pump or the engine..
 
Remove the three bolts holding the pump onto the frame(engine will ALSO BE LOOSE).
 
Bolt the engine back to the frame (likely will need some washers/spacers in place of the removed pump).
 
Run the engine alone and see what it does.  The pump can also be turned clockwise (looking down at it) with a pliers or vise grip. If the pump internals let loose, you'll feel it..
 
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Thanks for your response.  I was able to try this last night and it seems I'm having the same issue with the pump unmounted, so I guess it's the engine.