I just spoke to the guy I bought the boat from and he explained that the counter is there because it is a part of the specifications mandated by the military.
The engine which is military spec for some reason has a few additions on it which have also confused myself and others on different occasions and the counter is one of those.
It is supposed to display the amount of hours the engine has been running, however it's not working , thus my confusion.
I think it's actually a handy thing to have for the purposes of servicing, calculating fuel consumption etc. so I will try to see if I can find out how to get it working again.
Thanks again for your info.