Ok then don't need a pic. So heres the story, not the prop say, cause you may have no rubber on your prop. Then it can be the spring in the lower giving way, in simple terms, there is a spring that grabs, could give way would seem like a clutch slipping.
Could be the water pump shafts, but i don't think so i had that happen to me once they go they spin freely. it can be the coupler, but you have a one piece metal coupler no rubber.
The ball gears how do they look ?
So if the slipping occurs and the boat doesn't overheat, then i would lean towards the spring. See you still have water going to the motor, but if the water pump shafts went you would be overheating real quick no water going to the drive.
coupler went on me too also the motor overheated. And if the ball gears are slipping cause they are real worn down, then it would overheat.
thats the whole deal in a nutshell, it's up to you to take it apart, while your at it check the impeller i would just throw in a new one and housing. Need a cheap place to buy them send me a pm i'll send you the site.