Fusible link upgrade possible?

Do yourself a favor, and find a well-equipped marine supply store near you. Buy a resettable circuit breaker at the load rating you need and be done with it. Solder, a small piece of black tape and some heat shrink wrap will keep the moisture and such out.

I use all marine grade wire and electrical components in my cars. It's just higher quality unless you really know how to shop for quality auto grade stuff.