During the 15 years I've owned the E38, I have generally had excellent performance from the 5432 diesel engine. It drives the boat at 6+ knots (3-blade feathering prop) and runs smoothly. The engine is under the companionway and is closely confined in there (forward head and shower interior configuration, galley starboard aft). I have ventilation hoses run under there but no fans to cool the compartment. I have been using the Universal 160 degree thermostats continuously.
In its history, at approximately 2000 rpm cruise power, the engine warms up gradually. Once everything is up to temperature after 2-3 hours its coolant temperature is around 170-175 degrees F. The temperature gauge value has been roughly confirmed (+/- 5) using an infrared temperature measuring device pointed at the thermostat housing.
As the time at cruise rpm continues beyond 3 hours I usually see the temperature continue to slowly rise, creeping up to 180 and above, particularly in recent years. I control or stop the rise by throttling back 100-200 rpm. Cleaning the heat exchanger and clearing the strainer didn't change the situation. The Oberdorfer 202M-7 pump is old, but water flow is good and seems unchanged over the years. The 3/8 inch reducing elbows that are reported by one shop to be "standard" size for the Oberdorfer have a little calcium build-up. No bearing issues or anything with the drive mechanics of the pump.
These engine coolant temperature characteristics do not sound like what everyone else is experiencing, regardless of engine type or age.
At the beginning of our cruise this year, we limped in to Everett for a planned stop with a hot engine that required much more severe rpm reductions than usual. The apparent cause of the sudden worsening of the problem was a gummed-up and cracking seawater impeller. Cleaning that up and replacing the impeller returned the cooling to its usual gradually increasing self. I used a solution of Unchloric acid in the heat exchanger, which was needed anyway after seeing the condition of the impeller housing. All the impeller vanes were cracked. After some consultation, I decided to get some real engine flush solution (Fleetguard) and while I was doing that I decided to pop in the 180 degree thermostat that I had purchased as a spare during the 2016 engine problems (oil in coolant thread). So, I doubled the mooring lines on the boat and ran it in gear at 2000 rpm for almost 2 hours to make the flush solution work. Amazingly (or maybe as expected), the coolant temp rose quickly to 180 degrees (+/- a needle width) and stayed there the whole time.
The results of the flush were good, even super good. The flush cleared out more oil from the cooling section of the engine. The 180 degree thermostat tryout was wildly successful and it remained in the engine for the rest of the cruise with the same steady 180 degree performance (over a month and 120+ hours of engine operation). Below is a picture of the two thermostats. My tentative conclusion about this is that the physically larger 180 thermostat allows higher coolant flow through the system and that makes the heat exchanger more effective. I changed the two bronze elbows on the seawater pump to slightly larger diameter machined elbows, but other original bronze 3/8 inch elbows remained upstream on the strainer. I don't think there was any seawater flow improvement.
Put me, finally, in the group that recommends trying the 180 degree thermostat in the 5432, if everything else isn't helpful.
Do ya think this could be a problem?
In its history, at approximately 2000 rpm cruise power, the engine warms up gradually. Once everything is up to temperature after 2-3 hours its coolant temperature is around 170-175 degrees F. The temperature gauge value has been roughly confirmed (+/- 5) using an infrared temperature measuring device pointed at the thermostat housing.
As the time at cruise rpm continues beyond 3 hours I usually see the temperature continue to slowly rise, creeping up to 180 and above, particularly in recent years. I control or stop the rise by throttling back 100-200 rpm. Cleaning the heat exchanger and clearing the strainer didn't change the situation. The Oberdorfer 202M-7 pump is old, but water flow is good and seems unchanged over the years. The 3/8 inch reducing elbows that are reported by one shop to be "standard" size for the Oberdorfer have a little calcium build-up. No bearing issues or anything with the drive mechanics of the pump.
These engine coolant temperature characteristics do not sound like what everyone else is experiencing, regardless of engine type or age.
At the beginning of our cruise this year, we limped in to Everett for a planned stop with a hot engine that required much more severe rpm reductions than usual. The apparent cause of the sudden worsening of the problem was a gummed-up and cracking seawater impeller. Cleaning that up and replacing the impeller returned the cooling to its usual gradually increasing self. I used a solution of Unchloric acid in the heat exchanger, which was needed anyway after seeing the condition of the impeller housing. All the impeller vanes were cracked. After some consultation, I decided to get some real engine flush solution (Fleetguard) and while I was doing that I decided to pop in the 180 degree thermostat that I had purchased as a spare during the 2016 engine problems (oil in coolant thread). So, I doubled the mooring lines on the boat and ran it in gear at 2000 rpm for almost 2 hours to make the flush solution work. Amazingly (or maybe as expected), the coolant temp rose quickly to 180 degrees (+/- a needle width) and stayed there the whole time.
The results of the flush were good, even super good. The flush cleared out more oil from the cooling section of the engine. The 180 degree thermostat tryout was wildly successful and it remained in the engine for the rest of the cruise with the same steady 180 degree performance (over a month and 120+ hours of engine operation). Below is a picture of the two thermostats. My tentative conclusion about this is that the physically larger 180 thermostat allows higher coolant flow through the system and that makes the heat exchanger more effective. I changed the two bronze elbows on the seawater pump to slightly larger diameter machined elbows, but other original bronze 3/8 inch elbows remained upstream on the strainer. I don't think there was any seawater flow improvement.
Put me, finally, in the group that recommends trying the 180 degree thermostat in the 5432, if everything else isn't helpful.
Do ya think this could be a problem?