A few months back I posted that my 1980 merc,would not go up or down.After a few suggestions from on here,my friend rebuilt both cylinders.It worked in the driveway,but when I got on the lake,motor wouldn't move.This month my friend took the pump apart,it was full of gunk.So he cleaned it and it worked fine.While sitting in the driveway,i'd try the pump,every few days.The motor went up and down fine.This past Friday,I went fishing,and tried the motor before I left.Worked fine,got on the water,and motor wouldn' t move.Now from my house to the lake about 15 miles,what the heck,could have happened?