I have an older 2 stroke Yamaha 40 jet. The motor runs great but I seem to have a restriction in the cooling water flow. Last year while on the river I had some sand get in the cooling hose and was able to flush it there and get back up river. After that, I will get some water flow, then it may stop peeing and I would shut down the motor and let it cool. Once cool, the motor would pee again and then slowly stop as the motor got warmer. in the end I was making lots of short runs with a lot of bank time.
If you have any thoughts or ideas on what the issue or fix is, I would love to hear them.