[OM] Zuiko 75-150 mm f4 problem

[Helge M Tonning]

Got a nice good looking (8+?) Zuiko 75-150 f4 (nr 341xxx) with box. 
Only problem is changing focal length, requires sever change in distance. 
At 75mm - focusing on a subject prox 5 miles away, distance must be set to prox 
4 mtrs on the lens. 
At 150mm - focusing on the same subject, distance have to be set at prox 25 
mtrs.
What is wrong, and what can I do about it ???

(hope metric expressions dont cause too much trouble.....)

Helge