1989 5.8 omc wont go past 2500 rpm

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

Owners Manuel calls for AC MR43t with a .30 gap. I think I will tryy tha.t

That is the plug for the Chevy engine. It may be the same though.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

Yea the 5.7 calls for the same plug but .35 gap. Plug only changes with the 7.5 and 2.3l for 89 s

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

Like I said before, the fact that it is only happening at WOT is suspicious and it sounds like a lean condition. Spark plug change is easy though.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

Thanks for your help. I will try plugs first then mess with carb . I will update mon!

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

How are all your fuel filters? How old is the gas?

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

Just filled up at marina. I will change fuel filter as well .

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

How old and how much was the gas that was in there before you filled up?

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

Not sure. It's a marine quest marina so its suposed to be up to par.

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

No...I am talking about the old gas.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

It was fresh gas before I filed up at marina I had about 30 gallons of mid grade in there from shell with ethanol treatment in it. I ran it down to empty before filling up at marina.

 

[happyhitter]

Re: 1989 5.8 omc wont go past 2500 rpm

Please note that a wider gap is good as it means a more efficient burn for combustion, but the only down-fall is that it makes the coil work harder and that could be a problem (for coil) at higher RPM's. You might want to consider changing it for a newer one with more voltage output.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

Please note that a wider gap is good as it means a more efficient burn for combustion, but the only down-fall is that it makes the coil work harder and that could be a problem (for coil) at higher RPM's. You might want to consider changing it for a newer one with more voltage output.

Dist is an hei dist with 50,000 volts with upgraded plug wires. I'm puting the OEM plugs in today with about .45 gap and we will see how that goes

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

You need to find the equivalent heat range plug that is designed to gapped wider. You may have the side electrode is going bent at a weird angle to achieve the gap you are trying to get

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

replaced plugs with oem plugs gaped them to .45 runs great. gps speed said 32 at 3700 rpm on verry chopy lake. however when i pulled the champion plugs i found this. where did the rest of it go.

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

Looks like you had detonation due to improper timing or a lean condition.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

probably timing. i have adjusted it . any idea where the rest of the plug is

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

probably timing. i have adjusted it . any idea where the rest of the plug is

How far was it off?

You still need to pay attention to a possible lean condition. If its starts backfiring like it did before, you still may have an issue.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

Lean condition is adjusted on the carb correct? Any way to test if it is lean?

 

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

Lean condition is adjusted on the carb correct? Any way to test if it is lean?

You can't adjust the carb unless you change the jets. Assuming the carb worked at one time and is the correct carb and jets, the reason it would go lean is something clogging the jets, or something else in the carb or a fuel pump that is failing.

You have replaced all fuel filters right?

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

yes, fuel filters have been changed. today i was on the lake and it was a little smother. so i re checked my timing and it is at idle 650 and at 10 deg, at 4200 rpm it is at 31.8. is this correct for total timing? now i can only get it to about 3800 rpm and around 35 gps mph. i am not sure what size prop i have on right now. i took it off of my 88 omc 5.0. whatever they came stock with is what is on there. it comes out of the hole great and i am on plane in no time.
allso when i am runing at wot i start to here a slight taping sound coming from the engine. if i back off wot just a tad it stops. But , when i have the throttle cable disconected from carb and i reve it to 4300 rpm i never here the taping. i only here it when the throtle cable is atached going about 35 at 3800 rpm?