08 5.0 mpi (alpha 1 gen2 ) engine sputters initially under load but will clear up after some use. Cranks and idles fine though.

D

dsbunton646

Recruit
Joined
Apr 25, 2011
Messages
3
Toward the end of last season it started this sputtering/missing as fuel/throttle was applied. It is always on the initial use for the day. It will run kind of crappy for a short while and then eventually clear up and run perfectly. At first I thought I got some bad fuel in it. But after some seafoam, new fuel, and changing the spin on fuel/water filter the problems persisted....but always at first use of the day or trip. I've since changed the distributor cap, rotor, plugs and wires, as well as the spin on filter again. This time I poured the filter contents into a glass jar amd inspected it for water or contamination. The fuel from the filter seemed fine. I took it out yesterday after all that and fresh service and it still did the exact same thing but seems a little worse after having sat offseason.. After about 30 minutes it came back and ran fine. No stumbling anywhere in the throttle range. Maxed out WOT right where it should have after a little use. No stumbling when getting on plane etc...
Is there another filter I'm missing? Or any suggestions for me to try? I haven't checked fuel pressure butI suppose that's the next step?? Boat has about 160 hrs on it total.
 
alldodge

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
43,064
Could use a serial number of motor to verify what your configuration is?

Measure the fuel pressure at the rail, should be 43 psi at 1800 rpm. Should be close or slightly higher up to WOT
 
Q

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,348
Hi. Check the shift interrupt switch and adjust if need be. Mine and a couple of others I know of lately, have had such an issue. Especially when accelerating and/or full throttle. It can get momentarily nudged by the throttle assembly, then cuts the ignition to some cylinders.
Make sure that distributor cap is seated well too. And between the marks
 
T

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,911
dsbunton646 said:
Toward the end of last season it started this sputtering/missing as fuel/throttle was applied. It is always on the initial use for the day. It will run kind of crappy for a short while and then eventually clear up and run perfectly. At first I thought I got some bad fuel in it. But after some seafoam, new fuel, and changing the spin on fuel/water filter the problems persisted....but always at first use of the day or trip. I've since changed the distributor cap, rotor, plugs and wires, as well as the spin on filter again. This time I poured the filter contents into a glass jar amd inspected it for water or contamination. The fuel from the filter seemed fine. I took it out yesterday after all that and fresh service and it still did the exact same thing but seems a little worse after having sat offseason.. After about 30 minutes it came back and ran fine. No stumbling anywhere in the throttle range. Maxed out WOT right where it should have after a little use. No stumbling when getting on plane etc...
Is there another filter I'm missing? Or any suggestions for me to try? I haven't checked fuel pressure butI suppose that's the next step?? Boat has about 160 hrs on it total.
Click to expand...
You might have a coolant leak into a combustion chamber?
 
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