I have a 20hp Johnson 1997 that starts and runs great for about 10-15 minutes (sometimes less). Running across the lake wide open all is well and then all of the sudden it starts to stutter. I once it starts it continues until the engine cools off. 90 minutes or more. Then it will run good again until it heats up. I dropped it off at the marina for this issue last winter and the lot rebuilt the carburetor. Got it back and took it out Memorial Day. Same thing. I replaced the fuel pump and no change. I attached a short video of what it does when hot.
