Mercruiser 350 MAG MPI MIE SKI 0L305632 skipping

[wizard0356]

Tige skiboat --- engine started and ran fin when put in water 2 months ago -- now it appears to be "skipping", "Missing" as the tach will drop down and the engine sound like it did as well. Replaced all the spark plugs, new distributor cap, new rotor kit, distributor sensor, fuel filter and the problem persists --- gets worse as you try to increase speed/throttle

Tried to attach a MP4 video but it failed

 

[Scott06]

Tige skiboat --- engine started and ran fin when put in water 2 months ago -- now it appears to be "skipping", "Missing" as the tach will drop down and the engine sound like it did as well. Replaced all the spark plugs, new distributor cap, new rotor kit, distributor sensor, fuel filter and the problem persists --- gets worse as you try to increase speed/throttle

Tried to attach a MP4 video but it failed

What do spark plugs look like, by reading them you can tell a lot about air fuel ratio. Do you see this miss on a timing light?

Do you have strong spark on a gap tester

 

[wizard0356]

What do spark plugs look like, by reading them you can tell a lot about air fuel ratio. Do you see this miss on a timing light?

Do you have strong spark on a gap tester

Put in new plugs MR43LTS - the old ones looked pretty decent just got the gap tester will try that next - did not try timing light but you can see/hear engine miss --

 

[Fun Times]

Are you getting any warning horns associated with the skipping?

Any of the other gauges skip as well?

Make sure all wiring connection points are clean and tight.

Doing this hot or cold? or both?

X 2 on timing light testing too.

You may want to connect a fuel pressure gauge to the fuel rail schrader valve to see if psi is staying where it needs to be of 30psi,
item number 6 and 7,

Intake Manifold and Fuel Rails(SN 0L304600 & Up)

Intake Manifold and Fuel Rails(SN 0L304600 & Up)

www.mercruiserparts.com

350 MAG MPI SKI (GEN+) GM 350 V-8 1998 AND UP - 0L002600 THRU 0M310009

350 MAG MPI SKI (GEN+) GM 350 V-8 1998 AND UP - 0L002600 THRU 0M310009

www.mercruiserparts.com

 

[Scott06]

Are you getting any warning horns associated with the skipping?

Any of the other gauges skip as well?

Make sure all wiring connection points are clean and tight.

Doing this hot or cold? or both?

X 2 on timing light testing too.

You may want to connect a fuel pressure gauge to the fuel rail schrader valve to see if psi is staying where it needs to be of 30psi,
item number 6 and 7,

Intake Manifold and Fuel Rails(SN 0L304600 & Up)

Intake Manifold and Fuel Rails(SN 0L304600 & Up)

www.mercruiserparts.com

350 MAG MPI SKI (GEN+) GM 350 V-8 1998 AND UP - 0L002600 THRU 0M310009

350 MAG MPI SKI (GEN+) GM 350 V-8 1998 AND UP - 0L002600 THRU 0M310009

www.mercruiserparts.com

Agreed would look if fuel pressure is dropping.

would also think the crab cap but that was just replaced.

Is battery and connections good? seem to see a lot of issues with MPIs getting squirrely if battery condition is iffy.

 

[Fun Times]

would also think the crab cap but that was just replaced.

Just a quick reference point in regards to this design cap didn't really start until very late 2002 but considered 03 year model for the Merc marine side...VP too I do believe.

The serial number suggests this will be the distributor ignition sensor design,

Distributor And Ignition Components(SN-0L304600 And Up)

Distributor And Ignition Components(SN-0L304600 And Up)

www.mercruiserparts.com

Though the serial number is close enough that it could also be this design,

Distributor And Ignition Components(SN-0L304599 and Below)

Distributor And Ignition Components(SN-0L304599 and Below)

www.mercruiserparts.com

 

[Scott06]

Just a quick reference point in regards to this design cap didn't really start until very late 2002 but considered 03 year model for the Merc marine side...VP too I do believe.

The serial number suggests this will be the distributor ignition sensor design,

Distributor And Ignition Components(SN-0L304600 And Up)

Distributor And Ignition Components(SN-0L304600 And Up)

www.mercruiserparts.com

Though the serial number is close enough that it could also be this design,

Distributor And Ignition Components(SN-0L304599 and Below)

Distributor And Ignition Components(SN-0L304599 and Below)

www.mercruiserparts.com

ok didnt catch that neither of them are Crab caps one looks to be Delco EST , the other Thunderbolt

 

[Scott Danforth]

check the plug wires for arcing against the motor

 

[Scott06]

check the plug wires for arcing against the motor

Yes did not mention wires replaced, Should also double check firing order since cap was changed