My buddy's 15 horse Evinrude, model #15404 S, has started jumping occasionally when running in forward. When the skip happens, it sort of feels like the motor is hitting a log. This seems to be happening more and more often. His repair guy told him that the repair would be very expensive and it might be time to throw the motor away. (I told him to throw in into my yard.) Its a good running motor otherwise. Is this a bad gear in the lower unit? If so, is that lower unit interchangable with others? I don't have a book on this motor, but according to what I'm finding online, it seems that the lower unit is the same for a 9.9 up to the 15, but I'm not even certain of what year this one is. Any help is appreciated.<br />_Tom