My son left his 8hp Yamaha electric start connected to a battery. Start button is on tiller. In a heavy rainstorm his battery box filled with water and shorted the terminals. His roommate texted him his motor was making a horrible noise and disconnected it from the battery and the noise stopped. Now I have the motor and trying to ascertain the damage. I see the oil pressure light is red when turning it over (should be green). There is spark and compression however it appears to be low 145 lbs. It does not start or even backfire. Would appreciate any suggestions to aid in repair?