93 omc 5.0 efi wot bog

I

indigobluex

Cadet
Joined
Jul 22, 2003
Messages
14
Just picked up a 93 fourwinns 19 foot with a 5.0 Ford motor EFI starts good runs good but if you try to run wide open throttle for an extended period of time it will bog and start to spit and sputter. I have changed the cap and rotor and fuel filter and added some fuel treatment to the tank it will run all day at 4000 RPMs but the minute you go to 4500 wide open it will stay there for about 30 seconds and then start spitting and sputtering like it's running out of fuel I've also noticed the tachometer sometimes goes crazy goes up to six grand goes past 6 grand I don't know if they're related or just separate issues any ideas. I've read a lot of things on the 5.0 spitting and sputtering but they were all carbureted not many EFI Motors and none of them were wide open throttle most of the sputter issues that I've read about were 25 to 28 RPM
 
alldodge

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
42,957
Fuel pressure - Put a fuel pressure gauge on the motor and see if it falls off when rpm increases.
Tach - watch the tach and see if it starts jumping around
 
M

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Does the tach do that every time when the sputtering occurs, and only then? If not then probably unrelated.

You can check to see if the tach is affecting the ignition pulse signalling. You can isolate it from the ignition system, usually a gray wire connected to the minus terminal of the coil is the tach signal, disconnect that one. Rinse, repeat.

Could be the fuel pickup in the tank is compromised, or the antisiphon valve is not flowing as it should.

Could be mp is weakening. You can check the fuel pressure at the rail(s) when this happens, usually a schrader vavle is accessible. See if it is within spec.
 
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