Twin 5.0 efi loss of power

There is no shrader valve on these motors. Mechanic said i would have to install exactly what you sent.
 
That's a PIA. Have you ever cleaned the tank, tank pickup, and replaced any rubber fuel lines ? If it runs good then doesn't and runs good again, it's doubtful the fuel pump is bad. Could be crap in tank plugging the pickup and then clearing off.
I'd go through the fuel system from one end to the other, seeing it sat for so many years
 
Update. Went to change the fuel pump in the cool fuel gen 2. ( thanks merc for the easy placement) took old one out and at the inlet there ia a screen in the pump. 1/2 blocked with what looked like a paint chip. Put new pump ( after market p.o.s ) blew fuse and caused 3 hrs of headache to find fuse. Cleaned old pump and reinstalled. Sound much better. Taking out on mon and will keep u informed. Thinking paint chip would float around untill it hit the center and cut down fuel. We will see. Fingers crossed. By the way fingers are a bloody mess after working on the cool fuel gen 2
 
Well that didnt work. Took out and same thing. 1 motor runs fine other just hits 3000 rpm and drops off with more throttle to like 2500. Gonna plow out all fuel lines with air. Replace fuel pump and fuel regulator. Double check wires to make sure not crossed. Just weird that it ran great then ran like crap in same trip. I have twins with 1 gas tank. Pick up is welded in
 
Well tonight i took it out and had only a little problem with motor. Took a bit but plained off and ran great. Stopped and let ot sit for a bit. Started again and boom. Hit 3200 rpm. Gave more gas and rpms just start to drop to 2600 rpm. Still Thinking fuel. Any problem with blowing air in all the fuel lines, regulator lines before new install and down the pick up tube in gas tank? Not thinking tank cause i have twins and 1 motor runs good. After it runs crappy i took off fuel water seperator and full of gas. If pick up is clogged wouldn't it stop pulling gas to the filter. Any thoughts?
 
The last link has a likely cause, but...Reminds me of a lawnmower when you leave the choke on too long. Sounds like a mixture problem, but I dont know the EFI and if the fuel pump determines the amount of fuel/air at different throttle positions.

Found similar problems from different sites. Possible dropping a cylinder due fuel, injector, caps and rotors, or spark plug?http://www.marineengine.com/boat-forum/showthread.php?395017-mercruiser-5-0-efi-low-rpms

http://www.marineengine.com/boat-fo...-2002-mercruiser-5-0L-EFI-will-not-accelerate

This guy found a piece of debris in his fuel tank that would float around until it hit the fuel pickup...sounds most similar to you.
http://forum.chaparralboats.com/index.php?/topic/16423-mercruiser-50-efi-cuts-down-at-high-speed/
 
Final update. Its finally fixed. Thanks for all your help guys. 1st, i filled the water seperator with sea foam and ran it for 10 minutes at 2000 rpm. 2nd took out fuel pump and fuel regulator from cool fuel 2. 3rd blew all fuel lines out. 4th installed new fuel pump and fuel regulator. Runs like a dream now.
Problem was fuel pump was weak. Fuel regulator little filter was clogged. When i took off water seperator and blew through fuel line from fuel pump a wade of brown shit just blew out. Looks like i had a starving fuel problem at high rpms. These motors do not come with a shradder valve and could never get a fuel pressure from them. Thanks again all and happy boating
 
Had a similar experience, turned out there was a rusty ferrous fitting in the CF2 housing that was sending rust flakes to the pump and regulator. Brown = rust
 
If this is indeed the culprit I recommend getting fuel tank and fuel polished.

There are service trucks that come to dockside and suck all the fuel and circulate through series of filters and they suck up all the sediment at bottom of tank into the far corners.

I recommend this on all boats every 3-4 years. It removes any moisture in tank as well.

Good luck!
 
Jeff Delbuono said:
Final update. Its finally fixed. Thanks for all your help guys. 1st, i filled the water seperator with sea foam and ran it for 10 minutes at 2000 rpm. 2nd took out fuel pump and fuel regulator from cool fuel 2. 3rd blew all fuel lines out. 4th installed new fuel pump and fuel regulator. Runs like a dream now.
Problem was fuel pump was weak. Fuel regulator little filter was clogged. When i took off water seperator and blew through fuel line from fuel pump a wade of brown shit just blew out. Looks like i had a starving fuel problem at high rpms. These motors do not come with a shradder valve and could never get a fuel pressure from them. Thanks again all and happy boating
Click to expand...
Can you source your pump and regulator? OEM or Aftermarket?
Scoflaw, you know where I'm taking this..... ;-)
 
I bought an after maket pump first on e bay for $80. Kept blowing the fuse as soon as i tried to start it. took 3 hours and a qt of blood for this problem. Put old one back in for weekend. Had to buckle down and pay $340 for siara pump and $150 for merc regulator. Some times it pays. This time it did not.
 
Def plan on getting tank cleaned out this year. Im in nj and have to search for a company. When i pulled water seperator and dumped in glass jar at first inspection looked ckean and good. Let sit over night and thats when i saw the rust at the bottom.
 
I've had good luck with the aftermarket Airtex E11004 for the cf2. Think about it, your tank is either aluminum or poly and the pickup and sender stuff is all non-ferrous....so unless it's the filter itself rusting, which happens, where is all this rust coming from ?
 
True. Mine is aluminium. Boat sat 8 years on land before i got it last year. Replaced all injectors and other motor fuel pump last year and had no problem before this year. Will be put on the yearly to do list. Amazing how something so simple can cause hours of frustration. I did enough research on line and in books for the cause of my problem to be a merc master tech now.
 
I live in NJ and searched around for a company that does fuel tank cleaning and fuel polishing dock side with no luck. Has anybody ever used this stuff to clean a tank and how did it work.
Screenshot_20190603-144124_Chrome.jpg
 
Jeff, Thanks for referring me to this topic. Is it one fuel pump that services both engines? Because my issue is on both engines and I find it weird that two fuel pumps would suddenly go bad at the same time.
 
1 pump per engine. Check both the water seperators for gunk. You also have 2 seperate fuel feeds. Post what they are doing
 
Jeff Delbuono said:
I live in NJ and searched around for a company that does fuel tank cleaning and fuel polishing dock side with no luck. Has anybody ever used this stuff to clean a tank and how did it work. View attachment 70875
Click to expand...

If you look at the MSDS sheet for this product and you look up all the items it contains it's mostly Kerosene and it's not any different then their fuel additive.
 
This is also a good checklist. A nice kind guy put it on the site for this issue. I have read, searched, and done enough research to know that this is a common problem
Screenshot_20190530-164601_Chrome.jpg
 

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