Leaky pump pre filter housing

I bought an old farm property in Southern Maine that has a Gibralter 16x24 above ground. I do not think it has been used in five or more years judging by the amount of sludge and sand that was in the standing water below the discharge pipe. There is a horse training arena very close to the pool and i suspect that is where the sand came from.
The 3 port selector valve was replaced due to freezing water damage and the Jacuzzi 3hp pump has a horizontal tiny crack. I tried to use JB Weld and the leak re-appeared, I was wondering if anyone had a similar frost related crack and what type of resin fix was successful. I plan on trying fiberglass resin and glass fiber.