1996 Evinrude runs rough mid range

[cardedo]

I have a 1996 70 hp vro evinrude idles good and open throttle good but between 2200 rpm and 3300 rpm seems to have a skip once to 3300 rpm clears up and runs great. This is on a pontoon any ideas. Thanks

 

[jakedaawg]

Does the miss feel like an off and on miss, like a switch? Or is more spasmatic like fuel? You can hook a timing light to each spark lead and watch the flashes to see if they are even or skip around. It can be tricky to pinpoint these. At those rpms the timer base is already fully advanced I would think.

 

[ct1762@gmail.com]

Very well could need a carb clean! Intermediate orifices might be gummed up.

 

[havoc_squad]

If you can consistently get out of the hole by very slowly increase throttle out of the poor running, that's a dead sign you have carb issues.

I wouldn't do that much because it already sounds like a lean issue that needs to be fixed right away by doing a detailed cleaning of all carbs according to the factory OEM service manual steps. No shortcuts.

I would almost be sure that if the OP is at minimum idle speed in gear on the water and throws the hammer down fully on the throttle, the motor will stumble, cough, and show the classic symptoms to being way too lean.

The carb jet sizes are tuned to provide the needed extra fuel during transitions from going from idle to intermediate to full speed.

An intermediate jet clogged up will make the 2000 to 3000 rpm transition impossible or very difficult.

 

[cardedo]

Thanks for replies. No problems going from idle to wot just when cruising at Mid range seems to be a little skip.

 

[havoc_squad]

All things still point to a lean fuel issue. It is highly doubtful you have a spark issue if the motor idles well under load and handles full throttle RPM's under load fine.

If the link and sync timing was done correctly per OEM service manual steps, then it is unlikely you would have excessive timing which would cause pre-ignition/detonation risk.

You could be having one carb intermediate jet leaning out a cylinder, raising the risk of added cylinder wear and detonation risk.

When has the carbs been cleaned and rebuilt according to the OEM service manual steps?

Are you stabilizing your fuel and running it through the motor before long term storage of the boat? This is one of the best defenses against early E10 gas deposits buildup in carbs, that and buying no Ethanol gas if possible and stabilizing it.

A note though, if you pre-mix your gas and do not use the oiling system, some two stroke outboard motor oils do come with fuel stabilizers in them.

 

[cardedo]

Carbs have been rebuilt bought 2yrs ago was doing it when bought.I always run non ethanol gas and Seafoam will try cleaning and carb rebuild. Thanks

 

[cardedo]

Sorry carbs have not been rebuilt