John Deere F1145 Engine Questions

[mlenkowski]

I recently purchased a used F1145 in great condition; one owner, residential use, stored inside, well maintained, 1340 hours. This is my first F1145. I also have a F935 and 855 CUT. The F1145 is an early model based on the serial number. The engine in this model is the 3TN75, as opposed to the 3TN78 that was used in later models. I am looking to understand why John Deere changed the engine? Has anyone used F1145s with both the 3TN75 and 3TN78 engines? If so did you notice any differences? Both appear to carry the 28 hp rating, but the 78 is a bigger motor displacement wise, approximately 1.2 L vs 1.0 L. My 855 uses the 3TN75RJ engine as well but is rated at 24hp. I know that different injection pumps and rpm settings can lead to differences in HP production. Again I am just looking for perspective regarding the differences in engines used on the F1145. Thanks.

 

[mlenkowski]

Based on the F1145 technical manual, the 3tn75rj is in fact rated at 24hp. Therefore the change in motor did provide for 4 hp increase. The 24hp seems powerful as of now, I have a 60" side discharge mowing deck. All other components and features remained the same. I am still curious, is there a noticeable difference between the two power plants used on the F1145? If so and anyone has used both, how would you describe the difference? Thanks