Maybe one proposing name aboard boat? I don't know (7)
I believe the answer is:
kneeler
'maybe one proposing' is the definition.
(someone may go down on one knee to propose)
'name aboard boat? i don't know' is the wordplay.
'name' becomes 'n' (common abbreviation e.g. on forms).
'aboard' is an insertion indicator.
'boat?' becomes 'keel' (I've seen this before).
'i don't know' becomes 'er' ('er' is a hesitation).
'n' put within 'keel' is 'kneel'.
'kneel'+'er'='KNEELER'
(Other definitions for kneeler that I've seen before include "Hassock" , "Cushion in chuch pew" , "Church pew cushion" , "It supports bended joints (in church?)" , "Cushion provided in church" .)