Ditto a64 and Cheeckako. I would add, were they running at high RPMs? A lot of engines will be unbearably noisy when run at a high rate, but perfectly livable at a more modest speed.
So, look for a trawler with a single
six-cylinder, and don't try to push it past hull speed
. No, it won't be as fast as twin 3208s running wide open, but it will be far quieter and get you there just as reliably. Then make sure that it is well tuned, balanced, and everything is aligned correctly. That will take care of most of the other noises.
If exhaust noise is an issue, that's usually easy to identify. Vibration is the one that can be hard to pin down. Could be engine vibration, shaft vibration, prop vibration, transmission
, who knows? Good engine mounts can make a big difference, but you also need to try to get rid of the source of the vibration. If everything is running properly, aligned properly, balanced properly, there should be very little vibration to begin with.
You might also want to toodle over to trawlerforum.com, where you will find more trawler specific discussions. Good luck!