Wont go past 2500 rpm

[richw03]

1998 5.0 efi mercruiser won't go past 2500 rpm even if throttle is all the way forward.
Goes past 2500 in reverse fine
Idles fine
I have cap,rotor, plugs,and wires on the way
I'm at a loss

 

[Hookin.Bookin]

Just had a current issue like the with my Johnson after being rebuilt come to find out the wires coming off the power pack was on backwards causing it to idle rev and work in reverse, but soon as I’d go forward it would bog and not go over 2500.

 

[richw03]

Just had a current issue like the with my Johnson after being rebuilt come to find out the wires coming off the power pack was on backwards causing it to idle rev and work in reverse, but soon as I’d go forward it would bog and not go over 2500.

When you say power pack is that the distributor?

 

[Scott Danforth]

check the neutral safety switch. if the EDM thinks the motor is in neutral, the RPM wont go above a certain RPM

check fuel pressure. if you are TBI or MPI, there are different pressures.

 

[richw03]

Even if it goes into gear fine and is responsive from idle up to 2500 rpms when you give it throttle

 

[jimmbo]

1998 5.0 efi mercruiser won't go past 2500 rpm even if throttle is all the way forward.
Goes past 2500 in reverse fine
Idles fine
I have cap,rotor, plugs,and wires on the way
I'm at a loss

Did you actually check to see if there is an Ignition Problem, or are just going to throw Parts at it?
Higher Revs in Reverse, could be due to less load on the Engine, due to the Prop operating in the Exhaust Gases

A Compression Test should be done
How long have you owned this Boat?
When did the Problem develop?

 

[richw03]

I just got the boat 2 weeks ago.
I figured I'd replace all that I listed so I know for future maintenance.
I am going to check compression later today as well as check the injectors I'm just asking around for others input as far as someone having a similar issue

 

[Hookin.Bookin]

When you say power pack is that the distributor?

For my boat yes, just make sure your cap and wires are correct it could also be a neutral safety switch or if one of your water temperature switches are going bad you can unplug it and then see if it clears up and if it does replace that sensor

 

[FunInDuhSun]

Try changing the gas filter before anything else. I had similar symptoms many years ago and it was just a clogged filter!

 

[richw03]

It only has a water fuel separator filter.
I also installed an in-line fuel filter coming off the tank before the separator.

 

[Scott Danforth]

It only has a water fuel separator filter.
I also installed an in-line fuel filter coming off the tank before the separator.

why? that just adds restriction. the fuel water separator filter is a full filter.

 

[richw03]

Ya that makes sense I was just thinking more is better..lol
I'll remove it now that you mentioned added restriction.

 

[alldodge]

What is the motor serial number?

 

[richw03]

0L025063

 

[alldodge]

Thanks
Need to measure FUEL pressure by connecting Tee adapter at item 1 or remove item 3 at attach gauge. Pressure should be 30 psi


If you have a digital meter with tone or a 12V resistor LED can connect it to DLC connector. Turn key ON and do not start, then listen for tone or LED to flash. Count the flashes/tone and see if there are any codes


Should also check timing. If ECM is detecting a knock then it will reduce timing.

 

[richw03]

Does motor need to be running while checking fuel pressure?

 

[alldodge]

Does motor need to be running while checking fuel pressure?

Not for initial test, but with you being unable to go above 2500, will need to see if things change as RPM increases

 

[richw03]

Ok I spliced in a tee from my fuel pressure kit between the in tank pump and the fuel filter...
Have hose hooked up to muffs turned key to on position no change on guage..
Started it and it runs just fine still no reading on the guage I can see fuel spraying from the injectors
How the hell does that work?
Or mean?

 

[richw03]

Also it will rev over 2500 rpm but it's not under load being its in my driveway

 

[richw03]

Also fuel pump whines for a sec and then is quiet