Problem solved
When I installed the impeller, being alone at the time, I had assumed the proper rotation direction of the pump. I lubricated the impeller, bent a few of the "vanes" relative to the assumed rotation and installed the cover. Well, I was wrong - so the problem all along has been the impeller installed with the "vanes" bent and working against the proper rotation, so apparently it was just enough to reduce the pumps efficiency to move the seawater. Now, I did remove the heat exchanger and found what sounded like rocks inside, but turned out to be stones of some sort, from a calcium or element buildup, because as I bumped the exchanger, and shook it, the stones began to break apart. I then removed the drain plug and the pieces fell out. I also ran a wire rod down each of the exchanger's holes to be sure each was clear. Once re-installed and all connections secure I started the engine and now have the desired result. One more thing though, something I didn't mention on this forum, I couldn't install the e-clip on the end of the pump shaft, meant to secure the impeller I suppose, but it doesn't seem to affect pump performance. I believe I can slightly pull the shaft out enough to install the clip but I really don't see the need for the clip as the pump is self priming and the impeller is completely enclosed between the rear wall and the cover of the pump.Thanks for everyones feedback and If I can be of assistance please let me know - clancy151@cox.netWill