That is a nice and clean motor. Looks like you take good care of it. However, the video sure sounds awful. I agree that something wrong and glad you are pursuing it.
Can you provide more background and info about motor? Is new to you? Routine maintenance done? Etc. Also any issue you had in the recent past, like an overheat or loss of oil pressure?
Please provide as much info as possible and the good folks here will be able to help figure this out. In the meantime I do not recommend taking this boat out.
