Oh dear, oh dear - Pampulha, one of my (many!) travel regrets. We had bussed in overnight to Belo from Brasilia to start a 1 week driving tour of Minas Gerais. I had been told that Pampulha Airport was a good place to rent-a-car with better "deals" than downtown and early opening too. This was all very true - and thus it was that we merely did a quick tour by car of the Pampulha Lake (which is virtually next to the airport), seeing the various buildings from the outside only, before starting out on the 3+ hour drive to Diamantina and then returning to Ouro Preto that night - all far too rushed!
I can recommend the plan in every respect (including arranging to leave the rent-a-car at Santos Dumont airport right in downtown Rio!) except rushing Pampulha in that way - Big mistake!! The numerous Niemeyer Buildings around the lake could easily fill half a day or more.
So - I have no personal experience of getting inside the Yacht Club (As far as I am aware there is only 1 "Yacht Club" by Neimeyer at Pampulha!) but can confirm that it is easily viewable from the outside along the Lakeside circumference road.
I found this Web site of the "Iate Tenis Clube" which uses the building and it refers to Public tours of the Art works (which must provide at least a partial tour of the buildings) from Tues - Sun 11.00 -17.00http://iatebh.com.br/plus/modulos/conteudo/?tac=obras-de-arte
See the History section for more about the Yacht Club as part of the overall Neimeyer complex at Pampulha