1. Take the lower housing off.

2. find something to use, with a hammer, to drive the "pin" out that holds the grates in. I used a big nail, that I ground the point down.

3. Straighten the grates.....I've done the filing bit, that Cobble Crusier mentioned.

4. If liner, has lot's of "grooves"......get new one.

5. Make sure you count the number of spacers, if you take impeller off, write the number down......so many on top, so many on bottom.

6. If the edge of the impeller is chipped and looks like it would be filed, do so.....I found this for you....

http://www.outboardjets.com/pdfs/IMPELLERSHARPENING.pdf

http://www.outboardrepairs.com/topics/005416.html

7. If any big chips.......buy new......Stainless steel is the way to go....many new motors now have the stainless steel impeller, right from the factory. Choice is either a 3 or 4 blade, impeller, in general a 4 blade....more get up and go but less top end.

Good luck........I have a feeler guage that is 8 -10" long, that makes it easy to check spacing of impeller to liner. Too much space, poor performance......... to little, engine might not start at all, to tight or if could wear a groove in the liner....right away.

Liners are $40+ ...... impellers ...... spendie!!!!!!!