[77newell]

The mechanically governed engines benefit more from a pyrometer than do computer controlled engines. With a two-stroke Detroit Diesel engine the critical thing is to keep it wound up when under significant load. If you are running above 1800 RPM I doubt you can damage the engine due to high exhaust temperature. However, you do need to monitor coolant temperature since the heads are prone to cracking if they overheat. I never let coolant get over 210 degrees before downshifting and if it's headed upwards rapidly I shift early. It is a cheap price to pay to protect the heads. Depending on the health of the radiator this may or may not ever be needed. My previous 77 coach with a 350hp engine never needed downshifting other than to the engine speed up. The 93 coach with a 500hp engine and what appears to be the same size radiator has required downshifting due to rising temperatures a few times.