Hi guys,

I have a boat with twin 300 Verados and I am experiencing a very odd situation.

I start up both engines at a temp of 75F (ambient temp). after a few minutes one engine starts raising the temp leading to running temp whilst the other only varies with a few degrees. After around 5 mis the temp are as follows: 80F port engine / 140F starboard engine).
I checked the engine manually and the port side engine is as cold as when originally started whilst the other feel a lot warmer, so the readings and sensors are reading properly.
Another thing I noticed is that the port engine is idling at 600-650 rpm whilst the port goes down to 550.

I am suspecting 2 things, either a stuck open thermostat or else a thorn poppet valve.

I wanted to ask if anyone has experienced something similar.

Thanks for your assistance.

John