no baffels / oh and no water in the oil
what do you have as a breather on your valve cover, if any. Could be plugged. If you have a pvc valve it will do it. it builds up pressure and it has to go somewhere.
When it happened to me. i brought it straight home changed the oil took it back out and tried it again.
No luck same problem so i took back home changed the oil again and changed the breathers on the valve covers.
Took it back to the lake and it ran like a raped ape

My next trip was not so good. The motor said uncle

filled it up with water again. took it home pulled the top end off and two cracked heads. Now im on a mission.
I also wonder if it was my logs that dumped all that water in my motor? is that possible.
2sav