We replaced the fuel pump and rebuilt the carbs and it ran just fine, only took it out a couple of times. Sat unused for 4 days now the starter barely turns the motor over. Both batteries were checked and are good. Starter gone bad??
Remove the battery and bring it to any Marine or Auto store they will load test it for free and verify a full charge if all pans out ok then verify all your battery connections are LUBE and tighten correctly.
Is your engine equiped with a solenoid ? If yes this can be the problem also ..