150 EFI Mid-range Surging

[DBremer]

I have a Mercury 150 EFI. It idles fine and at WOT is runs perfectly. In the mid-range it has a extreme surge. With a steady throttle setting it will slow down, then speed up, slow down....................

I have discovered that the surging doesn't occur when the battery is fully charged using the on-board charger. After a day or two on a fishing trip the motor will begin to surge in the mid range. It seems like the motor doesn't keep the battery charged enough to prevent the surging. The only thing running off this battery is starting, boat console, livewell pump and bilge pump. Everything else; tolling motor, stereo system, electric anchor etc are run off a separate pair of Optima D27M Blue tops up front.

The motor has had new plugs installed, injectors cleaned, water filter replaced, both voltage regulators were replaced. The battery is a new Optima D27M Blue Top.

Any thoughts?

 

[ndthwacker]

Re: 150 EFI Mid-range Surging

Hey DBremer, i also have the exact same symptoms you do to on a 2007 60hp mercury efi 4 stroke and can not find a answer to my problem, i have not charge my battery and tried seen if that has helped like it helps you, kinda odd. i have also tried plugs and water filter and seafoam. The one thing i did find out today though is that my plugs that are recomended for that motor come stock with a differnt gap size then the manual calls for. u may want to look into that as i intend to check mine in the next few days and regap them and see what that dose. let me know if u find a sloution or what happens, and i will do the same