Hi
 I just got a 21 ft tahiti it has a 460 ford and Berkley jet , bought it from a friend and took it out sunday for the first time , it runs about 160 Degrees at slow cruise (30 ) and when I go to an idle after about a minute or so its up to 200-210 "   is there a impeller that may be bad that pumps water to the engine ? 
thanks
Bob