2009 Mercury 60 HP 4 stroke EFI will not continue to run when past idle

[bassman463]

Hello all, I have a 2nd owner 2009 Mercury 60 HP 4 stroke EFI Bigfoot S/N 1C102750 which has been giving me fits currently and progressively went from great to good to bad to worse over the course of the past few years. First time I noticed the problem 3 years ago it would occasionally "sputter" when full throttle. 2 years ago the sputtering was progressively worse when less than full throttle. Last year, even worse under less throttle. This spring, I could barely get it on the trailer. It will run on idle, but not much more. It is overwintered(South Kentucky) in a slip but was winterized with fuel stabilizer, etc. Also during those 3 years I did regularly change fuel filter, spark plugs and stabilize fuel for winter.

Last summer I installed new primer bulb and fuel line to tank, new plugs, new fuel filter and even drained the fuel tank(didn't see any water). Still has original black fuel line under the cowl. This spring I looked at injectors and VST. Injectors appear ok but I did not perform any additional testing on them other than just cleaning them. I moved on to the VST and removed the hp fuel pump and looked at the bottom screen. I think it looks filthy but would like others opinion, and if this enough restriction to keep it from running past high idle. The other small round screen at top of hp fuel pump was very clean and looked good. I did purchase a new bottom screen but I am not near the boat so I will not be able to try the new screen for a while. If this doesn't work, I am running out of options. I know I should wait to see if this works, and I will not try anything else until I replace the screen, but while waiting I wanted others opinions in case this doesn't work. BTW I struggled with what descriptive word to use so I chose sputter....I would equate it the same as "missing" but that term sounds like electrical which I do not believe electrical is the issue. Thanks!!

[EuropeanAM]

Welcome to BBC!

If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to provide the Required Info (serial number) when posting. Thanks!

You are likely on the right track... if you felt the inlet filter to the fuel pump was filthy, that would be the obvious place to start. Make sure that the connection joint where the pump attaches to the top of the VST is in pristine condition (often best to install NEW).

If problem persists, it would be wise to monitor fuel pressure and see if it is stable or falls off when the engine dies out.

Injectors on this model are bad about becoming restricted with congealed fuel... the injectors flow SO LITTLE fuel when working right that they become restricted by even the slightest amount of congealing.

[bassman463]

Thanks!! Edited post above and added S/N. I also attached a pic of the screen in the initial post, but I did a poor job of stating that..Thanks for the tips! Will see what the new screen does first, then start tackling your recommendations if needed. I will post what the problem/solution is once I get to the bottom of it! Thanks again!