1989 5.8 omc wont go past 2500 rpm

[bruceb58]

Re: 1989 5.8 omc wont go past 2500 rpm

I would take it out, run up to WOT, run for a few minutes and pull the plugs and do a plug read.

 

[Wind dog]

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?

So you have a ticking sound from the engine when under load @WOT?

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

update. ticking sound was because my timming was way off. i now have it adjusted properly and engine purs!!! thanks for all the help!!!!

 

[airdvr1227]

Re: 1989 5.8 omc wont go past 2500 rpm

What boat are we working on? I don't remember the exact pitch on mine...i think it's 17. I'll get 41-42 on GPS at 4400 rpms.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

This is an 89 Bayliner 2455 with omc 5.8 prop is now 4 bld aluminum 15x16 on rough water I'm at35mph GPS and 4000 digital rpm. I know I should be around 4500 rpm but can't get there even messing with trim and trim tabs. Maybe if it stops being windy down here I can test it on calm water.

 

[Idlespeedonly]

Re: 1989 5.8 omc wont go past 2500 rpm

Have you checked you plugs yet? As for the part of the plug you were missing it more than likely bounced around on the piston for a while then went out the exhaust. The picture of the plugs you posted look waaaaaay to lean.

 

[talies13]

Re: 1989 5.8 omc wont go past 2500 rpm

Have you checked you plugs yet? As for the part of the plug you were missing it more than likely bounced around on the piston for a while then went out the exhaust. The picture of the plugs you posted look waaaaaay to lean.

It does seam to be running Lean . I have a 4 bl quadrojet. How would I adjust.

 

[Idlespeedonly]

Re: 1989 5.8 omc wont go past 2500 rpm

If its lean dont run it. You can richen it up by changing the metering rods and jets.