This is a 1986 150ETXJ couter-rotating unit.<br />First, shifting into reverse would grind but not engage. Then shifting forward would grind but not engage. Now, no grinding sound and unit will not engage forward or reverse. Shift cable and linkage appear normal in operation. Over the winter, I had the lower unit off to inspect the reverse problem and on the bench it shifted fine and no indication of significant wear. Any Ideas? Do you think the lower unit needs to be rebuilt/replaced? How can I tell where the problem is?