91' 175hp EFI Idle is Low 400-500 RPM's

[Coleboessen@gmail.com]

I Just bought a 2004 Lowe Tahiti 220 Deck boat that came with a 1991 Mercury 175hp Xri. So far it runs great at higher rpm's just Idle's around 450RPMs...so when I put into forward or reverse it will die. Out of the water it will Idle higher but it will fluctuate up and down between 400 and 1200rpm's. A few nights ago I it backed into the water left it on the trailer and adjusted the Idle set bolt/nut and had it staying around 1100rpm's. Next Day we go out on the water and It is right back to 400-500rpm's. I did have the Fuel filter changed, replaced the Fuel line/bulb, and I topped off with ethanol free gas but it had around 20 Gallons of older gas in it before so I could only get about 10 gallons of fresh gas in it. Just wondering if any one had some suggestions of what to try? Maybe Fuel pump needs replaced (weak)? Any suggestions would be great. Thanks Cole

[boats.net]

Probably needs carbs removed and cleaned, replace intake gaskets and synchronize and adjust carb linkage.