Still rough idle. What should I try next?

[btravlin2]

Howdy......'95 Johnson OceanRunner 225. Runs lights out above 1200rpms, but not so smooth below. Here's what I've done so far:

-Rebuilt the carbs/throttle twice: everything in the kits plus the throttle/manifold gaskets. Second time to make sure. Both times I found all passages to be clean. Only slight improvement.

-Replaced the pricey VR02, pulse limiter, all fuel lines, filters, fresh gas.

-Replaced plugs.

-Seafoamed thoroughly according to the Top Secret file.

I haven't checked timing or compression.

At this point I can't imagine it being a fuel-related problem. So what should I look into next?

 

[James R]

Re: Still rough idle. What should I try next?

The three basics. Compressions, fuel supply and spark power. If it is not synchronized correctly it will not idle.

 

[metriccrescentwrench]

Re: Still rough idle. What should I try next?

The three basics. Compressions, fuel supply and spark power. If it is not synchronized correctly it will not idle.

+1.

I haven't checked timing or compression.

Don't spend another penny or put in an extra minute of your time until you make sure the compression is good. Those should have been among the first things you checked.

Assuming the compression is good you need to follow the factory service manual's procedure for doing a link-n-sync. It'll walk you through properly setting the idle timing, making sure all the throttle butterflies are fully closed at idle, and making sure the timing starts coming in at the correct point. Without all that being correct it won't idle well.

 

[btravlin2]

Re: Still rough idle. What should I try next?

+1.



Don't spend another penny or put in an extra minute of your time until you make sure the compression is good. Those should have been among the first things you checked.

Assuming the compression is good you need to follow the factory service manual's procedure for doing a link-n-sync. It'll walk you through properly setting the idle timing, making sure all the throttle butterflies are fully closed at idle, and making sure the timing starts coming in at the correct point. Without all that being correct it won't idle well.

Yes, I know now I should have done timing and compression first. I'll let a mech friend do them, and check spark too. I don't have those tools. I had hoped the carb rebuild would do it. It's fully linked & synced.....butterflies are closed.

I've got the manual, so I'll check ohms and volts as well.

 

[heftylefty]

Re: Still rough idle. What should I try next?

Did u ever get it fixed cause I have the same problem. I bought power packs and coils along with a rebuild on the carb. Plugs n wires were replaced. I got a 200 evinrude 1977.

 

[btravlin2]

Re: Still rough idle. What should I try next?

I found a plug wire today that, according to my Fluke, was passing no spark......infinite resistance. All the others were ok. I thought it was just me not getting a good connection with the probes, but nothing I did changed it at all. So, tomorrow I'll replace it and see if this was the problem all along.

The motor at idle always sounded like maybe a cyclinder wasn't firing. Why in the world I didn't start with plug wires I'll never know. Live n learn.

All other ohm tests were in spec to the manual.

 

[James R]

Re: Still rough idle. What should I try next?

I have been working on a 150GT 1984 fresh water motor and was amazed to find that all of the plug wire connectors at the spark plug end were badly corroded. I made my own new wires and idle is a little better.
However I found that using a spray containing fuel/oil 50:1 mix carefully sprayed into each individual carb throat whilst the motor is idling showed that I had one carb running lean. Unfortunately further stripping and cleaning did not improve the situation much so it looks like I am stuck with one carb a little lean on idle. A little extra oil in the mix will help I'm sure. I am running at 50:1 all the time so no worries about having a VRO going down to 100:1 and starving the cylinder of oil.