i have a 27 powerquest with a 502 mpi w/silent choice
when im cruising the boat has two different noises it runs smooth then gets a more dronning noise and keeps
going through this cycle the tach stays the same
this happens at fast and slow speeds is this related to the silent choice? it seems like its coming from the exhaust
when it runs smooth it seems the water is flowing through
the exhaust good then when it starts to drone it seems
like the exhaust is restricted

anybody else notice somthing like this

Is the noises only there when runnung through closed exhaust (silent mode) and not there when the exhaust is open???? Possible bad gimbal bearing??? Need more detail...

it does it in both modes of operation open and closed

I have a 26 powerquest with silent choice doing the exact same thing.

Were you ever able to diagnose where it was coming from

I know this post is old, but thought I would give it a try.