Here is a long, engineering version of the answer - I don't know.
An engine applies several significant forces to the transom (mounting plate). The weight of the engine pushes down. When powering the boat forward, the propeller is both pushing the bottom of the transom forward and simultaneously pulling the top of the transom aft. These forces are transferred through the transom to the center log, and through the center log to the horizontal crossmembers and from there to the deck and the two outer logs. The net effect is that the center log is trying to lift the front of the boat up and push it forward while gravity is trying to push the nose down, and drag from the water is trying to push the outer logs aft.
All this means the maximum horsepower your boat can safely carry is determined by the weakest link in this chain of structural connections. A good engineer with accurate details about the layout and materials used in your boat could calculate a good answer. In lieu of that your best bet is to see what other people with similar setups have done. If they have been running a 200 HP engine for several years without problems, you will likely have a similar experience.
