Bad gas mileage in 2001 Sundancer (340)

[Scott_2001]

Is anybody having an issue with gas mileage in a 2001 SeaRay dancer with twin 6.2 ltr engines? My boat is only getting about 1/2 mile to the gallon. This is half of what I got with my old 1989 dancer. I have replaced fuel filters. My port engine is also struggling to get rpm's also. I think these two problems are related. I recently took a 75 mile trip on my boat and burned 140 gallons of gas. I'm told I should be somewhere around 90. I am cruising at 26 mph @ approx 3900 rpm. Any input would be greatly appreciated.