Nelson Marek 43
Nelson Merek did not design the 43. They designed the 45. I have seen the 43 ascribed to Ted Brewer but I have also seen this denied as well so it is not clear who designed the 43. The 43 is a heavy, center cockpit cruiser/aft cabin cruiser. They are reasonably good boats that were reasonably well constructed. They sail well for what they are although are useless as sailboats in lighter air. They can be found quite cheaply but a lot of these boats ended up in the charter trade and I believe they were also marketed as Hirsh 43''s as well.
The 45 began life as a grand prix level IOR era race boat. They were constructed in three levels of finish from an out and out racer to a very nicely finished centerboard cruiser. There was a club level race boat that fell in between. In their day they offered reasonably good performance but came with all of the problems associated with an IOR design. This is especially true of the Centerboard versions which had substantially higher center of gravities than the deel fin keel full race versions.