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1995 350 Magnum Tournament Ski Throttle Body EFI Fuel Strangulation

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pwskicat

Regular Contributor
Hello all. Still trying to get this TBI engine to run @ WOT. A previous owner removed the OE Vapor Separator Tank, substituting an aftermarket electric fuel pump incapable of the fuel delivery required to run to WOT. Top speed is supposed to be 43mph. and the engine starts missing and running hot @ 34. To date I've:

Downloaded the correct Mercruiser Service Manual
Changed fuel filter
Cleaned fuel tank and replaced fuel
Checked MEFI-1 ECU for codes: None
Confirmed mechanical lift pump pressure (6 psi)
Installed an high-pressure electric fuel pump that can meet fuel delivery spec
Confirmed electronic ignition is operating to spec
Confirmed all sensors are operating to spec
Confirmed fuel pressure at TBI is correct (30 PSI constant)
Moved fuel return to a portable fuel tank to rule out a restriction on that fuel line
Called multiple Mercruiser shops who have never even heard of, much less worked on this engine

Pretty sure it's fuel starvation. Thinking about taking the mechanical pump out of the system, and moving the high-pressure electric pump to a "push" position close to the fuel tank. Right now, it's mounted on top of the engine, close to the throttle body. It has to suck the fuel through the fuel filter, which may be part of the problem, and its current location is very hot, which may be another part.

Pls don't tell me to "throw a carburetor on it." That's not an easy swap, requiring a whole new ignition system as well. Nobody makes a kit, and I don't have the expertise to build one. If you're not here to help, please don't waste our time. Thank you.

PW
 
I recall your posts from last year on this, very diligent troubleshooting work. Can you post a link to the old posts so we can see the whole thread?

anti siphon valve at tank outlet was ruled out right?

If I recall the vst vst was a float operated resvior that contains the high pressure pump? If so perhaps moving the high pressure pump close to the tank as you outline is best next step
 
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OK time to start eliminating the possible trouble spots. Use a small fuel supply above the HP pump inlet to bypass the fuel tank and lift pump and go for a test run (preferably still tied to the dock) to see if that improves things.
 
o2batsea said:
OK time to start eliminating the possible trouble spots. Use a small fuel supply above the HP pump inlet to bypass the fuel tank and lift pump and go for a test run (preferably still tied to the dock) to see if that improves things.
Click to expand...

Will try to do this in the next few days. The weather in Michigan this June has been so rainy, that I've exactly once, and farmers here are facing huge losses because the ground is too wet to plant.

What do you mean "still tied to the dock"? If I succeed in getting the boat to run at WOT under load, it would tear my dock off its moorings. Pls explain. Thank you.
 
pwskicat said:
Will try to do this in the next few days. The weather in Michigan this June has been so rainy, that I've exactly once, and farmers here are facing huge losses because the ground is too wet to plant.

What do you mean "still tied to the dock"? If I succeed in getting the boat to run at WOT under load, it would tear my dock off its moorings. Pls explain. Thank you.
Click to expand...
Hm. Sorry you have a wimpy dock. Yeh, I tend to not test my stuff away from shore as I hate having to figure out how to get a dead boat back home.
 
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