Been using trolling bags for years. Tie them off correctly and it should get you down to 1.2 . They come in various sizes. Get two of the same with line on each end. Best bet without adding anything to the engine. I troll during the summer and drag two of these all day. Keeps a 30ft Sportcraft at 2.5 that runs about 4 or so otherwise. The other option is a 9.9 horse 4 cycle kicker beside your big engine for fuel saving.