Yam 15 Spark Plug Inquiry

[Sea Rider]

Hello all, can someone tell me which is the correct factory delivered spark plug for: Yamaha 15 HP, 2 strokes model 2005-E15DMHL

NGK-BR7HS-10 or BR8HS-10 ? first is slight hotter than second one. In case first one is the correct, what would be the issue of using a slight colder plug, the engine is used at mid range to push a 30 footer sailboat.

Thanks in advance.