5.7 acceleration issue

[Chris5280]

Just put my OMC Cobra + 350 Chevy in the water for the first time of the season. Pulled drive and lubed, replaced plugs and cap/rotor when dewinterizing.

She backed out of the marina OK, but when I put her in forward gear, she sputters, backfires and stalls. Messed around with the neutral safety switch, but could only her her to stay alive in drive with the slightest throttle. Any more, and I get puffs of smoke through the flame arrestor. Reverse seems better.
What's wrong? Any thoughts?

No issues in neutral, BTW, or running on muffs in gear.

 

[Levinz11]

Re: 5.7 acceleration issue

The last sentence of your post would lead me to the lower shift cable. Sounds like it may be hanging up and activating the ESA (only happens w/boat in water). Have someone look at the ESA switches while you are working the remote to verify.

Do you have points or elec ignition?

 

[Chris5280]

Re: 5.7 acceleration issue

The last sentence of your post would lead me to the lower shift cable. Sounds like it may be hanging up and activating the ESA (only happens w/boat in water). Have someone look at the ESA switches while you are working the remote to verify.

Do you have points or elec ignition?

I believe electronic ignition. How would I know?

Does that mean I need to replace the shift cable, or just adjust it?

 

[Levinz11]

Re: 5.7 acceleration issue

I believe electronic ignition. How would I know?

Does that mean I need to replace the shift cable, or just adjust it?

Well, when you changed the cap and rotor, what was underneath the cap? Points (mechanical) or an electronic module?

The cable probably needs to be replaced. You need specials to replace or adjust them. You will also need a factory manual. Search eBay for "OMC Shift Cable Adjustment Tools".

 

[Chris5280]

Re: 5.7 acceleration issue

Well, when you changed the cap and rotor, what was underneath the cap? Points (mechanical) or an electronic module?

The cable probably needs to be replaced. You need specials to replace or adjust them. You will also need a factory manual. Search eBay for "OMC Shift Cable Adjustment Tools".

Looks like an electronic module- pic attached. So, I removed the two screws holding the esa sensor (the one with the trip arm) and pulled it off to the side to see if a bad shift cable was tripping the ESA. The engine still choked, backfired and stalled with the switch removed. The overstroke switch has both wires cut, so it has never worked I guess, but the boat has worked fine up till this season so I guess it's not necessary.

I adjusted the cable per the service manual this evening but haven't put it back in the water afterward. Should I still replace the lower shift cable, or does the ESA switch experiment point in another direction?

Thanks for your help.

 

[Levinz11]

Re: 5.7 acceleration issue

You have points ignition. They should be changed annually along with the condenser. They are a throw away part and a tune up kit is very cheap.

Unplug the ESA module. Black box about the size of a deck of cards. Mine is mounted by the port exhaust manifold. Follow the wires from the switches. If it stops backfiring/choking you may have found your issue.

http://www.iboats.com/OMC-Sterndriv...0778170--session_id.748109969--view_id.268980

 

[Chris5280]

Re: 5.7 acceleration issue

You have points ignition. They should be changed annually along with the condenser. They are a throw away part and a tune up kit is very cheap.

Unplug the ESA module. Black box about the size of a deck of cards. Mine is mounted by the port exhaust manifold. Follow the wires from the switches. If it stops backfiring/choking you may have found your issue.

OMC Sterndrive/Cobra Tune Up Kits - iboats

Thanks- is there anything special about the points/condenser for "marine" applications, or can I pick them up from the local auto parts store for a Chevy 350?

Couldn't get away from work in time today, but I'll try to take her out tomorrow and unplug the ESA module.

 

[Levinz11]

Re: 5.7 acceleration issue

Auto parts stores get weird when you say "marine". But no nothing special about them.

 

[Chris5280]

Re: 5.7 acceleration issue

Auto parts stores get weird when you say "marine". But no nothing special about them.

Disconnected 2 wires to ESA module and adjusted shift cable per manual. Took her out today and still the same issue. Also occurs in reverse if I rev high enough now. Idle still fine, or at low rpms under load.

Seems to rule out ESA switch, ESA module and shift cable.

Picked up points/condenser tonight and will install. What else could be causing this?

 

[Levinz11]

Re: 5.7 acceleration issue

Perform the full tune up. Set dwell, timing and finally idle to the manual spec. Report back.

Next on the my list would be checking out fuel delivery.

 

[Chris5280]

Re: 5.7 acceleration issue

Replaced coil, points and condenser; set dwell and timing. Had to increase idle to keep engine alive at only 4 degrees advance timing.

However, no improvement on the original problem. She still backfires through the carb and stalls as you add throttle from an idle, in gear only.

Also pulled anti siphon valve at fuel tank and checked, and also the paper filter at the carb. Fuel pump was replaced last year.

I'm at a loss.

 

[Chris5280]

Re: 5.7 acceleration issue

Could this be a carb issue? It seems most carb issues are at idle, where mine idles fine, but has issues as the throttle is opened. Any point in replacing the carb, or should I be looking in another direction?

Help!!

 

[Levinz11]

Re: 5.7 acceleration issue

If you're confident the ignition and ESA are good...the next logical step would be fuel. The feed from the tank is good, pump is good, filters are good. All that's left is the carb.

I decided to rebuild mine when: applying throttle quickly it would really stumble (almost die) then catch and go. If I applied throttle slowly it would gradually gain RPM and speed. When I pulled it apart the accel pump was rusted and almost falling apart. Carb kits are cheap and my 2 BBL was very easy to do.

 

[HCMQA]

Re: 5.7 acceleration issue

Could this be a carb issue? It seems most carb issues are at idle, where mine idles fine, but has issues as the throttle is opened. Any point in replacing the carb, or should I be looking in another direction?

Help!!

Actually, most carb issues on these cobra boats are not at idle but when trying to apply throttle under load.

Everything you describe sounds like you need to rebuild the carb.