just for fun, look here, I'm not to certain that piston damage is from the water pump. Looks like the carb was plugged, but I'm only seeinf one piston.
http://www.smellofdeath.com/lloydy/piston_diag_guide.htm

This is a good site if you get stuck
http://www.themarinedoctor.com/cgi-bin/YaBB.pl
see the vidios bottom right

and for parts breakdown if you need it
http://www.crowleymarine.com/parts.cfm
by year or serial #

keep up the good work