your question needs more detail - make and HP of engine would be a good start.
1. tipped on the muffler side or 2. blown engine
blew engine cause of low oil.... junk the mower engine & replace or pitch the whole mower... your choice
Replace the engine...End of story.
It just unscrews from the motor
If you mess with the governor you will probably blow the engine up. Change sprocket ratios or replace the engine with a bigger one.
Your mower has an electric PTO clutch that is worn out. It clutch stops working when it gets hot. Replace the PTO clutch and you should be fine. Expect to pay about $150 for the part.
Lack of compression
There are several reasons why your mower will not start. There could be an obstruction in the blade, a petrol mower could be low on petrol or the fuse could have blown in an electric mower.
If it is a riding mower it may have a blown fuse. They are usually located near the solenoid.
remove it, get a new one and find out what the gap setting is for the one you replace/ your size engine
There are 2 long "wires" with springs on them attached to the carburetor. One goes to the governor which looks like a small lever that comes out of the engine. If you are thinking of disconnecting it to make the mower run faster - DON'T DO IT!! You will be risking a blown piston rod and lots of internal damage to the engine.
To swap an engine on a Murry riding mower, it is important to make sure that the new engine is the right match for the mower, by checking the model number. You also need to make sure that the bolt holes line up, so that it will fit safely. Remove the old engine, and then replace the new engine, tightening all the screws and bolts in the reverse order that you followed to remove the old engine.