the pump impeller and housing are mounted to the lower drive unit if you are good with your hands and understand how things work. buy a manual for your motor its easy for mechanically inclined. but simple mistakes will kill your motor and drive.the lower drive is drained of gear oil if oil is milky you have a bad seal. if clean drop lower unit there will be a long vertical drive shaft that stays mounted to the drive. locate all o rings seals and gaskets a replace with new impeller and lock key is located under water pump housing remove cover and inspect parts rubber impeller usually wasted/cracked or melted from lack of water. replace with new cover. follow instructions like they are written also check pick up screens and remove to clean barnacles and debris clean water passages. never run engine dry it takes 15 seconds-to start tearing up new impeller good luck
The impeller on a 9.8 Mercury outboard boat motor can be easily changed. Remove the retaining bolt. The impeller will come off. Reverse the process to install the new impeller.
What year? It may require special tools.
right behind the prop, on the same shaft
The water pump impeller on a 7.5 hp Mercury outboard, is located on top of the gearcase, and is driven by the driveshaft.
You will probably have to drop the lower end of the outboard. Its sound hard but really it is usually quite simple. The pump is nothing more than rubber impeller on a brass collet.
Change the water pump impeller, they get old and need replacing every 5 years or so depending on wear.
see this site http://sites.google.com/site/bf50impellernotes/
Synthetic Rubber
Every two years to be safe
change impeller or check for blocks in water lines
18-3085 sierra
Sprinkle liberally a vile of gypsy tears