Hello all. New to this site and have a few questions. I just purchased a 1978 Searay 18.6 with a 305 V8 MerCruiser. It runs hot when plained out, temp comes back down when idle. The previous owner told me he had lower unit impeller replaced because it was bad, and it still ran hot. He also replace water pump on engine. He thinks some of the impeller debris, or other fourign material causing a restriction somewhere?! Is this possible? If so where should I be looking? Anything I may be overlooking? If the outdrive need to be serviced, is it a big job? Thank you in advance.