88 force motor stalled

I was having trouble with the motor dying out when at low idle. I got the idle adjusted and thought it was running better. I took it out Sat. the 85 hp is on a 45 foot houseboat. Did wonderful leaving dock didn't die once. Problem was after running for about 15 minutes parked in the cove and motor started dying between forward and reverse again. Sunday seemed to be ok again when left but it stalled after running for 15 minutes back to dock slowed down at no wake. Then wouldn't even turn over. I took cover off of motor and for lack of any clue. Hit the side with the wrench, moved the wheel to make sure not locked up. Then got it started, but when docking the monster it dyed when needed to put in reverse. Any ideas?? Thanks