The payload rating of the truck is always the important thing to look at. If the payload rating of the truck exceeds the pin weight of the trailer and the "stuff" you carry in the truck, then the SRW is all you need. Payload ratings of any truck, SRW or DRW, varies a lot depending on configuration; cab, bed, engine, drive train, even wheels/tire size.
The boat does not add to the 5er pin weight. In fact, it will actually reduce the pin weight some amount since that weight is sitting on the back of the 5er.
Do your homework on numbers.