Watch a video on youtube to see how it's done. If you are careful when taking the pump apart, you can get away with just using the impeller. Have you changed the oil in the foot yet? There is a allen screw on the very bottom of the foot towards the transom. Do not remove the straight screw on the bottom side of the foot, It holds the shifting mechanism in place. Check for water in the oil, if you have water contamination, it will need seals. Also google on how too drain the oil from your Force 125 HP. Let the forum know what you find out. Other's on here will answer your questions if you have problems.