As Bill pointed out, it's legal for Hams to modify their rigs
. Not so for Marine operators. The Marine Certification for the M802 would certainly be voided by the act of "opening" the set.
Note that the Icom User Manual does not mention how to open the rig
. It is not intended as a normal function. Clearly it would not have gained Marine Certification in this mode.
Note also that the M802 is NOT certified in Europe and doesn't have the CE approval.
To be legal as a Marine Radio
in the "Open" mode, the set would need a higher level of certification (GMDSS/SOLAS) and the operator would need a General/First Class certificate.