2.5 shutting down on decel.

[peedeerooster]

I have a 2.5 260 on an Ally drag. Been running great for 2 years except for power paks last year. Has Mercury digital EFI box with A48 chip. The fuel system has been flushed and new fuel filter. All 100% gasoline/no ethanol fuel. Fuel pressure is 41 at idle and drops to about 38.5 if I punch it. The engines cranks and idles fine. The engine with accelerate great and runs strong on top end. The problem is that when decelerating at around 15 to 25mph, the engine dies dead as can be. As soon as the boat stops, the engine will start fine and run great as long as i dont decel back down to this speed range. Is this a manifold pressure/EFI box issue or something I have not thought of. Thanks for any ideas.

[Jay Smith]

If you have your rig set up to start in gear I'd try idleing the motor up a bit with the idle timing, some 260's with the slotted attachment at the buttery fly has too cold idle timing.

I adjust ALL the slack out of the slider so that when the throttle is touched the butterfly moves. I then adjust the WOT stop so that the butterfly is now to be horizonal at WOT , next adjust the SMALL idle timing screw near the middle of the timing arm assembley so that your main upper timing bumper is 1/4" from the block timing boss.. I find the motor to be allot snappier on the bottom and the flame front to be now hot enough when the motor is snapped back to idle it will remain running burning the dense charge. I like idle rpm on 260's that are set up to start in gear about 1200 ish out of gear..

Hope that solves the issue.
Jay

[peedeerooster]

The slider does have a lot of slack. That is the throttle area that it is dying at.

[peedeerooster]

Thanks Jay. I will give it a shot.