Was fine. Sat up for several months. Backed it off trailer in R, shifter stiff. Quickly shifted into F to avoid dock. Grinding and clanking sound. Shift to neutral and start over. No prob. Now every third or fourth time shifted, the clanking and grinding happens. Lower unit? Cables? Not a great mechanic but a decent parts exchanger. Is it safe to operate or is this a fix NOW prob? Thanks.