What sort of boat? Any information?
 

O so my grandad had this old boat, I finally got around to picking it up and it's in rough shape. Found out that it was in fact non rc but was just started and let run. And it has a 2.5cc model Diesel engine which I haven't heard of before. I haven't run an rc boat before so I'm going in with only experience from about 3 years of flying rc planes. From what I've managed to find is that it should be a 1960's cabin cruiser??? It is missing the cabin obviously. My aims are to get it running again, probably with electric and components from hobbyking if possible. How would I get rudders going on it? Order a set from another boat and bolt it on the back? Any help will be appreciated

The back view, the grey colour, and what appear to be depth charges say some sort of patrol boat to me. Some of the markings on the deck look like the re might have been armaments sited there. So not a cabin cruiser, but no reason why it should not become one.
Rudders often come with a tube and arm, fixing is usually fairly self evident when the hardware is to hand. Measure how deep the prop reaches below the bottom of the hull. The rudder doesn't need to go deeper.

We'll that would explain this then. Also what could these kite shaped bits of brass be? One has some sort of glue on one side? Countersunk holes in both? And the second pic of the first lot I posed is of one of the rudders. Would any rudder unit work on the boat or should I look for a wide rudder if that is the correct term?