i can hear a pst..pst..pst..pst..when thw motor is running in the water...you cant hear it with muffs on it..has to have back preasure on it...sounds like exhaulst to me...this is a 2004 150 BRP powerhead on a 175 intruder frame...was just put togather and i noticed the sound the first time in the water..does it sound like a powerhead to exh. housing gasket..or maybe a loose bolt..where else could exh. sound come from..thanks for any help..