4PHM-TE exhaust, heat exchanger

[ttolly]

folks, this boat has been in fresh but going to salt. The raw water from the exchanger exits via exhaust. Can that be rerouted, or is it needed for back pressure? If the latter, is there a way to flush those areas in the exhaust system that the raw water contacts? Same Q for the exchanger. it appears that salt water circulates through the core of the exchanger, rather than the main body of the exchanger (the t-stat apparently is in the mount below the main cooling component--see diagram below). So wondering if a way to drain the the raw when not in use