Hi from New Zealand,yes you can get them rebored and get bigger pistons,but youve got to look at cost versus age of motor.outboard parts are horrendously expensive to repair,so to rebuild your motor could cost more than a good secondhand one.Ive just bought a 1998 DT65 Suzuki outboard for $1600,hyd tilt,tidy condition,been o/hauled,whereas a good s/h outboard is normally about $5000.So I got a v good deal.Yours is 25yrs old,so unless youve used it exclusively in fresh water,corrosion is the big factor in assessing whether its worth o/hauling.check out s/hand outboards in yr area,see what sort of money they go for.