I have a 1990 OMC Cobra out drive hooked to a 5.8 L Ford V-8. When I shift into reverse gear, it bogs down the motor and makes it sound like it is surging. (loading up) After about 5-10 seconds it will finally get better. It does not grind going into gear, but is does severly load down the engine for about 10 seconds. Reverse does not work when the engine is bogging down. Any thoughts?