06 vmax hpdi sounds weird while in neutral

Link is a video of the sound it has while in neutral. Boat ran fine but when its put into gear the noise goes away. Ive never had a vmax so not sure. Powerhead was replaced and new high pressure pump put in. Looking for advice before i buy. Thanks!!

https://youtu.be/nT-KUrEvxoo

It only idles in neutral on four cylinders until you put it in gear then the other two start firing.