Engine choking. Can't go over 2000 RPMs.

Yareck

Yareck

Member
Jan 18, 2014
82
Fort Lauderdale
Boat Info
1996 27' SeaRay Sundancer
Engines
7.4L MPI Mercruiser w/Bravo III Drive
I have 1996 MerCruiser 7.4 MPI. When I accelerate my engine is choking and won't go over 2000 RPMs. Pressure on the fuel rail is good 40psi
What can be wrong? Injectors?
 
Fuel filters, cool fuel filters, worn spark plugs, clogged injectors, motor in Guardian Mode
 
When this last happened to me it turned out to be water in the fuel. Siphoned tank out, replaced fuel filter, all better. It was able to rev up in neutral, but not underway.
 
Spark plugs are new, new water separator fuel filter, I connected external fuel tank with a fresh fuel. Still same symptoms. My mechanic told me to use sea foam gass additive to clean injectors. I'll do that tomorrow and run the boat all day. Will post what happens.
 
OK...my MPI has a fuel tank on top of manifold that holds a high pressure fuel pump.....a sump as I think it is called. It supplies fuel to rails. It would idle fine and all was good, but at RPM and load, would sputter. Took top off sump and removed high pressure pump and found the final filter screen covered with gunk. Removed and sprayed with carb cleaner till screens were clean and reinstalled. Problem solved.....My boat had twin 7.4 MPIs...with 400 hours when this happened. Be careful removing top of the tank as there is a very fragile O ring around the top that is very expensive. feel free to call me 314-703-9710
 
I ran my boat for 6 h yesterday with a sea foam gas additive but it did not help. I will look in VST vapour separating tank to look if it's clogged
 
Last edited:
its the filter in the upper tank.....while you are at it change other fuel filters....
 
Another guess on her Filter. I ran mine real low on fuel and it wouldn't rev over 2k underload afterward. Removed cool-fuel filter to find trash. Replaced with new. Seems to idle smoother. Then I Pulled the boat unexpectedly (Hurricane) and didn't get to sea-trail.
 
Are you sure this is a fuel problem? For what it takes, I would have a look at the flappers in the top of your Y pipe. Make sure they haven't got damaged and dropped down causing an exhaust restriction. Could also check your timing at higher rpm's to make sure you are not losing it and confirm it is advancing correctly.
 
Hi guys! Sorry I left for so long.
So mechanic came with a computer and read MAP and TPS sensors bad signals. I replaced MAP sensor first and nothing has changed. Next up will be TPS sensor. Gotta wait for it couple of days.
Boat cruises so I've been using it 2 times a week but can't go WOT.
I will post results
 
jonsm114 said:
OK...my MPI has a fuel tank on top of manifold that holds a high pressure fuel pump.....a sump as I think it is called. It supplies fuel to rails. It would idle fine and all was good, but at RPM and load, would sputter. Took top off sump and removed high pressure pump and found the final filter screen covered with gunk. Removed and sprayed with carb cleaner till screens were clean and reinstalled. Problem solved.....My boat had twin 7.4 MPIs...with 400 hours when this happened. Be careful removing top of the tank as there is a very fragile O ring around the top that is very expensive. feel free to call me 314-703-9710
Click to expand...

Yareck, Did you ever try this?
 
Yes it's a VST vapor separating tank. I will check that screen next. Thank you for your tip
 
So today I finally changed the second sensor(TPS) and things did not change. Called my mechanic for Tuesday.
Boat still cruises under 2000 rpm but can't go faster. WHAT CAN IT BE?
 
Also when I accelerate over 2000 RPMs I can hear backfiring and I can smell the gas
 
You must log in or register to reply here.

Forum statistics

Threads
113,234
Messages
1,429,027
Members
61,117
Latest member
jingenio
Back
Top