so I have a few problems that need major attention. First of I have a 20 hp godevil lt and it runs full throttle out of water and bogs down once it's back in the water and I give it throttle. It all started after I had changed the oil the night before. Idk what's wrong and I need some opinions. Next problem is I changed out the starter (it was a bitch) and after reassembling everything when I start it it no longer needs to be out of the water to start and the kill switch doesn't work and even worse when I turn the key off it just sounds like it turns one cylinder off. It's really weird and I have to like trick it out and make it kill it's self to turn off. What the hell did I do wrong

There is a level switch(mercury type) on the side of the motor. It could have moved. If no other problems just readjust it to an angle that keeps it from starting when in the water. If you look your kill wires come to a common point on an insulated post, it could be the problem there. Disconnect those and start motor, ground 1 wire at a time if the "circuit" are good the motor will tell you that the coil is grounding out, if not then you will have to check under the cowling for the problem. But it sounds like best guess, that the mercury switch has rotated for it to crank out of water, and possibly you forgot to hook up a wire or not grounding one of them not to kill the motor, both coils should be grounding when turning off the key.

Too much oil can cause the motor to kill under load.

Dirty carb can cause the bogging as well