There are 13 words that start with 'mains'.
| mains | mainsail | 
| mainstay | mainsails | 
| mainsheet | mainstays | 
| mainsheets | mainspring | 
| mainstream | mainsprings | 
| mainstreams | mainstreamed | 
| mainstreaming | |
Note: These 13 words that start with 'mains' are found from the USA & Canada version of the tournament Scrabble word list.