I have a 2003 Blazer boat with a Yamaha 225 Vmax. It has a Yamaha Vmax 25 pitch prop.
Issue: When engine is cold engine will turn up to 5400 rpms.
As engine warms up it drops back down to 5100 rpms. Recently took to Yamaha engine repairs. They checked
fuel pump, 02 sensor, tube behind 02 sensor, fuel line, rail pressure & all checked out fine.
Even the 'winky blinky'could not detect what is wrong. It gave no error codes. Any ideas as to why the rpms
drop after the engine gets warm?