Engine change

Sir, I have installed Rotax 914F on Stemme S6 aircraft, I have to change engine and arranged a used overhauled engine from one of my friend,

I am confused about changing of TCUaTCU engine hours counter,

Is it compulsory to change Tcu and eng hour counter with every engine lchange , If not then how to configured new engine with old TCU and engine hours counter,

More over there is no information about used engine change in installation manual.

Regards, khan