Can old Boat trailer tires hold the boat weight for 60 metres ?

My 25ft boat Trophy is in a marina and I did not use my boat trailer for 6 years ,the trailer was parked on a sandy parking near the beach .Now , and after 6 years I want to use the trailer to take my boat to the workshop ( about 60 metres from the slipway ) I inflated the tires and they look fine but one of my friends told me although they look fine they will go flat once the boat put on them ) I am confused now because I do not want to put new tires because I use the trailer may be once or twice a year . the question is do you think the tires can take the weight of the boat or they will explode once the boat on top of the trailer . thank you for your assistance.