"Replace the impeller and make
"Replace the impeller and make sure the water passages are clear of anything. Remove the shift cable from the mechanism on the motor and see if it will go into forward when you shift it manually. If it does, you'll need to adjust or replace the shift cable/mechanism. If it still won't go into forward, you have other issues that will require some disassembly of the gearcase. Since the impeller needs to go anyway, it's a good time to do this, too if you havea an Alpha drive. The Bravo and older big blocks have the raw water pump mounted on the motor but I would check out the whole raw water system, including the oil cooler if it has one."