Just remember what ever you buy, you said your on a boat and you will need tools you can depend on in an emergency. So what ever your selection is, remember to get quality and durability, stranded out at sea with heavy waves pounding you trying to get a engine back up sucks and sometimes every moment can count. It's like taking a spot or an ACR plb with you 100 miles out in the ocean, which one has the best chance to get you home. Cost Vs Reliability.