What type of battery should I get for my boat, 18 foot bowrider?

so the battery is old and has to go, currently in it, is a 12V deep cycle trolling battery. This boat does not have a trolling motor, or any electronics that really work, other than a fish finder that pretty much stays turned off. Should i get another deep cycle battery? or just a starting battery? It has a 90 hp Force outboard engine.