You need as much weight as possible in the bow . I have read where you may need as much as 200 + lbs. to get it to track correctly. The V of your hull WHEN in the water will keep it tracking in the direction you want it to go. Right now it sounds like you have yourself,engine,fishing gear and probably batteries ,gas tank all in the stern, that translates to your bow not making enough contact ,so the prop thrust is pushing her in circles. Sandbags and or moving as much gear and batteries to the bow should keep it tracking straight. One other option is trolling bags on both sides and then bumping up your speed, or if it keeps going to.the port throw one bag on the starboard side to compensate or vise versa. Trolling bag,not drift bag. You could try a 5 gallon bucket with some 1 " holes drilled in the bottom.to see if that helps before you buy bags. Secure midship so the bucket doesn't get sucked into your prop.Bucket should end up about 1-2' in front of transom..