Recently purchased an old town Aquarius 170 with a 3.0 liter OMC Cobra. When I'm "driving" it chugs and seems to want to stall. If I put it in neutral it seems to run okay. The guy I purchased it from said when the gas gets low it does it more often. I have about a 1/4 tank currently and that's when it started. Any observations or suggestions would be helpful.