Hi Tony,
Thanks for your reply, the marine Engineer was very busy so just told me it is canal water cooled and also has a tank with antifreeze for the heat exchanger. I only have my camera phone and as it is very murky here and does not have a flash I don't think the pictures would be of any value, but once I find my proper camera, I will take some pictures to finally know 100% what we have.
It was my confusion, the water pump is a big brass type run from a separate belt to the alternator, and from looking the engine also has a normal car type water pump that flows the water/antifreeze mix around the system.
I am taking her up the river later, so when I have the engine covers up will give the camera phone a go and see how they turn out, thanks again for your help, I do really want to bottom this out.
Cheers
Geoff