Trolling speed issues.

I have a 2001 bahacruiser 286 sportfish w/ a 8.1 liter Volvo penta I/0 (400 hp I think). I've bought the largest beefy bags Amish outfitters sells (one on each side obviously). Had the maps sensor replaced/fixed and still having trouble getting below 2mph when trolling. Any ideas on how to get her slower besides shelling out the pesos for a kicker motor?

We have zf transmissions with trolling valves they work great but still pricey

the only thing I can think of that might work is to manually turn the idle screw down if your motor will run at a lower rpm. i.ve done it on a couple of mercruisers I've had. but I really know nothing about your set up.

Thanks for the info. I will look into it.