I recently did the same thing. Old motoguide12/24 to a 24v 80# thrust. I tried using only 2 of the wires. It worked but wires got pretty warm and would blow 40a fuse. Decided that was just too much current for that gauge wire.
Rewired it all. I bought some 8ga Ancor brand wire and 50a circuit breaker, found best prices on eBay. I didn’t use the 4 prong up front but replaced with this https://www.tracoutdoor.com/shop/electrical-items/trac-high-current-connector-kits/
Probably invested under $100 total and put 2 hours or so into install. But it looks good, works great and I know it’s fine right. Pm if you want more info