Lady M: Exhaust Cooling System

During LADY M’s maiden voyage, the high temperature exhaust cooling alarm sounded. I immediately maneuvered to a safe spot and shut down the engine because who knows what it could be when you first buy a boat. After tracing out the Lehman’s cooling system, I found that everything was lined up correctly with all coolant levels sufficient, so, ????. I threw in the proper coolant + water mixture used by the previous owner to top the tank off and while doing so, found the air bleed valve previously left open. Though meant to purge air from the system, an open air bleed valve while the engine was running allowed air to get sucked into the cooling system and become entrapped. Consequently, it resulted in a high cooling temp and set off the alarm. 

Note: never trust a previous owners work to be done correctly. 

I run a 120hp Ford Lehman 6 cylinder Diesel engine. These are known to be bullet proof and last well beyond what a typical marine diesel would (if maintenance is done adequately). The first rebuild cycle isn’t until 10,000 hrs. American Diesel Corp carries all the parts needed for these with some great helpful info.