5.7 mpi stuttering and no power

[walleye seeker]

2003 mercury mpi 555 ecm 350 mag.

Here is the problem. I take boat out get it ready for season first day runs beautiful.

Bring boat home decide to change my ex flappers {rattling}they are the old style 1 pc oval. y pipe is attached to an mr drive housing.
Take boat back out another day wont hardly run

My engine is hooked up to alpha 1 gen1 drive that is connected to an even older bracket at transom i beleive mr its a 1986 crestliner sabre

Did i install them backwards when you look down the y pipe the are open. if water were to rush in from back they would close i beleive this to be correct. If i flipped them over the ex would push them closed.


Also another post i pointed out i found 1 of the screws holding down the distributor cap is broken not the screw itself but the hole it screws into on the distributor my quick fix so it wasnt moving aroung was to zip tie the cap to the distributor which is working fine.

I have the smartcraft gauges and i am not getting any faults but it wont let it rev past 3500rpm . so it sounds like it is restricting my rpm or limp mode. no other messages come up.

I pulled plugs they are nice and tan and dry. Boat fires right up and idles nicely


What am i missing

 

[Bondo]

Re: 5.7 mpi stuttering and no power

Ayuh,... Check the contents of the fuel Filter, then Replace it....
My guess is, you picked up some Water...

 

[dannyual767]

Re: 5.7 mpi stuttering and no power

If the only thing that you changed was the installation of new exhaust flappers between good engine running and bad, that's where I'd look first.

 

[walleye seeker]

Re: 5.7 mpi stuttering and no power

Ayuh,... Check the contents of the fuel Filter, then Replace it....
My guess is, you picked up some Water...

The motor has 2 spin on fuel filters and both were changed before my first trip out. I pulled the ex elbows and both flappers are correct according to the mercruiser manual.

Another thing i thought of these mpi motors are very voltage sensitive would that be correct. I left the key on for 3 days with the battery switch on dual. I charged them enough to get her started and headed out. could it be my batteries are just to weak. i figured once running the aternator would take over,

 

[walleye seeker]

Re: 5.7 mpi stuttering and no power

BONDO you got me thinking i have a 4 stroke kicker motor teed into my main gas line . I was having a hard time getting the primer bulb to prime this spring . i wonder if the bulb went bad allowing air to be sucked in the fuel line

 

[walleye seeker]

Re: 5.7 mpi stuttering and no power

Well you were darn close bondo. It was sucking air through primer bulb for kicker.Blocked line and runs like a top again. I am going to replace the primer bulb and install a tee shut off valve . so it cant suck air there in the future. Thanks for the help.

Time to go salmon fishing on the great lakes