WE have over 7000 hours on the third tach in our 1855 and has had a rebuild more than once. Far as the oil cooler goes ours has a add on the goes between the oil filter and the base with coolant lines coming down to it. When we were using it hard we added a second circulation pump and drew oil from the bottom of the pan and thru a second oil cooler we mounted on the grill. This seemed to help more than anything.