Yamaha 300 Overheating?

[OnIsland]

2013 Yamaha 300. Was getting overheat sensor alarm on starboard engine. In some cases was happening quickly under acceleration or higher rpm after a short period but most times happens after long duration. (2hours at 3400 RPM) was due for a service anyway so replaced water pump and thermostats. No change. Engine pisses water from indicator at idle and up to about 1500 rpm. Then stops pissing above that. The moment I drop to idle it pisses again and if I increase rpm significantly ie 42-4500 rpm it pisses again but not consistently. Oil pressure indicators show normal. When I flush engines w hose at dock pee indicator does not piss. What questions do you have….I need help figuring out what is going on and what to do next? Can’t wait to hear what you all think. Thanks in advance!!