Mechanical Components that we can afford

Wow, great post Jackie. I understand the concerns about controllability, and I agree that it is important to be both fast and controllable.

I found some motors on Jameco's website that seem to fit our needs: 15k-25k rpm, reasonable torque and current, and low cost:

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&sub_attr_name=Current+%40+Max.+Efficiency+%28A%29&position=1&productId=237391&catalogId=10001&refineType=2&refineValue=10+%3C%3D++%3C+50&app.products.maxperpage=15&storeId=10001&refine=1&history=xqw5jp9m|subCategoryName~Electromechanical%2B%252F%2BMotors%2B%252F%2BDC%2BDirect%2BDrive^category~351530^categoryName~cat_3515^prodPage~15^page~SEARCH%252BNAV&ddkey=http:StoreCatalogDrillDownView

This one takes 13 amps, but would be very powerful, and it's only 6 bucks. (18krpm)

http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_232101_-1

1.43A, 23krpm, $3

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&productId=2082177&catalogId=10001&freeText=H615-66430&app.products.maxperpage=15&storeId=10001&search_type=jamecoall&ddkey=http:StoreCatalogDrillDownView

1.44A, 18krpm, $2

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&productId=232047&catalogId=10001&freeText=MD5-2445&app.products.maxperpage=15&storeId=10001&search_type=jamecoall&ddkey=http:StoreCatalogDrillDownView

20krpm, 2.05A, $3

http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&productId=211246&catalogId=10001&freeText=RC-260RA-2670&app.products.maxperpage=15&storeId=10001&search_type=jamecoall&ddkey=http:StoreCatalogDrillDownView

18krpm, 0.15A, $1, weak sauce

I'm a fan of either the beast 13A motor if we think we can handle the drive circuit, or the 20krpm 2.05A motor for a good mix of affordability and speed.

As for propellers and shafts, I think we should get decently large propellers and long (maybe flexable) drive shafts so we can keep the motor out of the water.