I worked for 2 different CAT dealers on industrial engines and generators, and on occasion some marine engines. All diesel engines are slower to warm up because at no load diesel exhaust temperature is very low, compared to comparable gasoline or natural gas engines.
The 3208 is slow to warm up in all applications but the high HP marine pleasure craft ratings are especially slow to warm up. This is because the cooling system must be designed for the maximum HP heat load, which means the cooling system is way oversized for light load applications like low speed warm up at trolling speeds, where the power generated is only about 5 HP or so. The only thing that will warm it up faster is more load, if you can run it up to about 1400 RPM in displacement mode, it should be developing about 40 HP if it idles about 700 RPM at 5 HP. At 1400 the engine is developing more power and higher exhaust temperature helping it warm up faster.
If slow warm up is a problem, you could add a Jacket Water Heater to the engine and partially warm the engine before starting. 3208s usually start well in cold weather and a JWH is not a requirement for propulsion engines, (required for standby generator sets) but pre-warming the engine to 100-120°F will do no harm and will dramatically cut warmup time required. A properly installed 1500 watt JWH should fully warm the engine from room temperature in about 4 - 6 (?) hours. The Kim Hotstart TPS151GT10-000 should do nicely if properly installed.
Hot water is lighter than cold water, and that is what pumps the water from the heater into and out of the engine. The thermostat turns on the heater when the inlet water temperature is 100 °F or less, and turns off when the inlet temperature reaches 120°. The outlet water temperature is not controlled and rises based on the flow of water and the power of the element. Ideally the temp rise will be about 40-60 °F. Poor circulation can Increase the temperature rise, and maximum water temp above 200°F will shorten hose life and can lead to rupture, so silicon heater hose is preferred. This is why proper installation is so important. Engine mounted Inlet and outlet full port ball valves are desirable in case a hose or heater starts leaking or ruptures, depending on how much room is available for installing them.
The TPS151GT10-000 heater must be installed vertically with the heater outlet below the engine water jacket inlet, with no steam traps or horizontal runs in the water line to the engine. The heater will make hot water and steam, so it is important to have a smooth upward slope with no traps to the engine inlet. The return water line can be installed in any fashion necessary so long as it is full with no entrapped air. It may require priming depending on how it is installed.
You want the hot water to enter the engine water jacket as low as possible on one side, with the heater return water coming from the water jacket on the opposite side, ideally both will be as low on the water jackets as possible with the inlet water away from the engine thermostat, preferably towards the rear if the engine. The return water line can be mounted higher, but it will take longer to heat the engine properly. If the heat in and the cold water out are not directly in to the lowest parts of the engine water jacket near the bottom of the cylinders, the engine will not heat effectively, or in some cases may not heat up at all. The idea is for all of hotwater and steam to put their heat into the bottom of the block for the most efficient heat transfer, and the cold water should also come from the lowest point on the opposite side, so that the coldest water is drained from the block and sent to the heater to be warmed.
I have been working on engine generators since 1979, and have installed and repaired thousands of JW heaters over the years. Some of you may find them to be of use in this application. If you install one properly it should significantly reduce the warmup time on your 3208 propulsion engine.
I hope this helps. Pete.
