An exhaust gas temperature gauge is often installed by owners along with a boost pressure gauge to monitor performance and load on a high output turbocharged boat engine. If you know what to look for you can diagnose some problems before they get too bad.

But they don't do much (certainly not the boost gauge for a normally aspirated engine. An EGT gauge might tell you if your water injection elbow is plugged or you are significantly over propped but there are other ways to check this.

David