Re: 4.3 mpi throttle problem
Then you should find a new shop that will run it on the lake for you. B/C Maybe the shift interrupt switch is bad or out of adjustment or has a vibration and making it run like that.Also some one should be running the boat at the time it does it so they can start testing it out and trying and looking at things as it does it, like the fuel psi, the timing, ect, Also you should have a leak down test and a compression test done to the engine.
http://www.harborfreight.com/cpi/cta...emnumber=94190. Also it Could be something like this Black Sensor Failures in MEFI-3 Mercury Distributors Used
on V6 and V8 305/350 cid Engines
Models
MCM V6 4.3L EFI Sterndrive Engines: S/N 0L360000-0M019879.
MCM V8 305/350 cid EFI/MPI Sterndrive Engines: S/N 0L331599-0L335999.
MCM V8 305/350 cid EFI/MPI Sterndrive Engines: S/N 0L340000-0M019762.
MIE 350 Mag MPI Ski and Inboard engines: S/N 0L302200-0L671800.
NOTE: Black Scorpion Ski engines are not affected by this problem because they use the
Delco EST ignition system.
Situation
Two ignition problems have been reported with the black sensor used on these model
engines. They are; ?a no start condition? or ?a rough running condition?. The most common
problem is the ?no start condition?.
Correction
No Start Condition: Before looking anywhere else on these engines, check for spark at the
ignition coil. If there is no spark, the most likely cause is a failed ignition sensor in the
distributor. Troubleshooting Chart in Service Bulletin 99-2 or the latest service manuals that
cover MEFI-3 on these engines can be used also.
Rough Running Condition: The engine will not run very well above idle rpm. Sometimes it
takes several minutes of running time before this condition occurs. Check all the common
causes for an engine to run rough, such as fouled spark plugs. If these all check good,
replace the sensor.
Most of these sensor failures are caused by a ?voltage spike? that occurs in the ignition
system. To prevent ?voltage spikes? make sure the positive and negative battery cables are
clean and tight at the engine and battery ends.
IMPORTANT: The battery cable terminals should be the type that clamps around the
battery post, not wing nut terminal connectors. If wing nut connectors are used at the
battery post, remove them and use a lockwasher and hex nut instead.
Make sure the distributor sensor bullet connectors are seated firmly into the engine harness
bullet connectors after changing the sensor.
IMPORTANT: To make sure that the ?fingers? on the rotor/sensor wheel do not touch
the sensor when the engine is cranked, follow installation directions.
Page 2 During installation, push the sensor outward until the rubber gasket is slightly compressed
against the distributor housing then tightening the sensor mounting screws.
77072
c
b
a
d
a
a - Mounting Screws
b - Rubber Gasket On Sensor
c - Distributor Housing
d - Push Sensor Outward
Part Required
P/N 87-861780A 2 Sensor Assembly-Distributor.
Order these parts only if damaged during removal.
P/N 13524A 6 V6 Rotor/Sensor Wheel.
P/N 13524T 1 V8 Rotor/Sensor Wheel. well this is just
some stuff that could make it run like this. Good luck with it let us know on how you make out in the end.
