Yanmar 4JH3-THE

[Jeanneau 45.2]

My 2000 4JH3-TE consistently overheats if run for more than 15 - 20 minutes at 2850 RPM or higher. I also have the PYI feathering MaxProp, and upon reflection think this may be my issue. Will speak with PYI before my next haul out. Fortunately I have the settings recorded from the last maintenance disassembly.

Another thought. Could it be that once I reach hull speed, the work required of the engine increases exponentially, and hence over heating? I guess I better check what my hull speed is and compare that to the speed through water (not RPM) and over heating.

[daletournier]

Originally Posted by Jeanneau 45.2

My 2000 4JH3-TE consistently overheats if run for more than 15 - 20 minutes at 2850 RPM or higher. I also have the PYI feathering MaxProp, and upon reflection think this may be my issue. Will speak with PYI before my next haul out. Fortunately I have the settings recorded from the last maintenance disassembly.

Another thought. Could it be that once I reach hull speed, the work required of the engine increases exponentially, and hence over heating? I guess I better check what my hull speed is and compare that to the speed through water (not RPM) and over heating.

You can adjust pitch in the water on mine. Quite easy to do if you have a hooker.

[svlamorocha]

Originally Posted by Jeanneau 45.2

My 2000 4JH3-TE consistently overheats if run for more than 15 - 20 minutes at 2850 RPM or higher. I also have the PYI feathering MaxProp, and upon reflection think this may be my issue. Will speak with PYI before my next haul out. Fortunately I have the settings recorded from the last maintenance disassembly.

Another thought. Could it be that once I reach hull speed, the work required of the engine increases exponentially, and hence over heating? I guess I better check what my hull speed is and compare that to the speed through water (not RPM) and over heating.

You are trying to invent a wheel that may or may not work. The tried and tested process for this starts by checking what is the maximum rpm that your engine will reach at full throttle in gear aka 'WOT rpm". If it does not reach rated rpm then start by cleaning/adjusting/replacing prop until engine can reach rated rpm. If it does, then look at the cooling system.

The logic behind this is complex but you don't need to understand all that to solve your problem. The summary is that if the engine maxes out betwen max torque rpm and max power rpm then the torque demanded from it (which drives heat production per revolution) is higher than design. Cooling capacity is proportional to rpm and cooling requirement is roughly proportional to rpm x torque demanded by prop at that rpm. These engines are designed with little slack in the cooling system so that they can overheat when overproppped.