Checked my Heat Exchanger today by removing both end caps and examining end chambers and tubes for blockage or contamination. Seemed all OK after removing lumps and scraps of old Zincs and some seagrass. Replaced Zinc, started and test ran the engine and observed very poor flow of cooling water from the exhaust. Temperature did not go above 160, but this concerns me. What steps should I follow to investigate this problem? Thanks for your knowledge.