2004 5.0 MPI Mercruiser

[Packers4ever]

Hey everyone, I have 500 hours on the motor, up until now everything has ran great - this week the motor started stumbling/hesitating every time I would accelerate from a stop, once on plane it ran well. I put a bottle of gas line antifreeze in hoping I had some water in the gas but it didn't help.

Any advice would be appreciated.

Thanks!!

 

[Bt Doctur]

fuel water/sep filter , clogged tank vent, hi pressure fuel pump going bad, injectors clogged.

 

[Scott06]

fuel water/sep filter , clogged tank vent, hi pressure fuel pump going bad, injectors clogged.

In additon to these I would also look at the ditributor cap- the crab style mpi caps are known failure points

 

[achris]

Being an MPI you'll need to connect a diagnostic computer. Your fault could also be the idle air control valve or the tpi faulty or out of adjustment... Yeah, you need to connect the computer..

Chris ...

 

[Packers4ever]

Thx for the input everyone!! ill change the water separator first - ive never changed the plugs either - maybe I should change those. Ill get it scanned.

 

[Packers4ever]

Anyone know what plugs to use or have recommendations?

 

[achris]

NGK ITR4A15

 

[alldodge]

It might not be the distributor cap, but they fail often and suggest to start there. The cap can look great and be bad

 

[QBhoy]

Typical symptoms of the diz cap failing. So common. Check your filter first off though. Plugs which run best are the NGK 5599 iridium plugs. Minimum spec but nothing like as good, are ac delco 41-993 platinum. Check you have these in there for sure. All too common for the odd guy to presume these take the same plugs as any old gm v8. They don’t run worth a crap unless they have the right plugs in them.