1987 OMC 3.0 jerks or stalls for a split second when cruising at 3000 rpm

[fmizell@95842]

Engine jerks and then runs normally for 10-15 minutes and then repeats..Have not determined cause yet but having Carb rebuilt and converting to electronic ignition in hope that will cure the problem. Has anyone experienced this?

 

[HT32BSX115]

Re: 1987 OMC 3.0 jerks or stalls for a split second when cruising at 3000 rpm

Engine jerks and then runs normally for 10-15 minutes and then repeats..Have not determined cause yet but having Carb rebuilt and converting to electronic ignition in hope that will cure the problem. Has anyone experienced this?

Howdy,


I think you should determine the cause before you start replacing systems.

If the engine appears to quit/starve, etc regularly, it could be fuel related. If fuel tank vent line is partially plugged, it will restrict fuel flow and possibly cause what's happening.

Try running the engine on a different fuel source. (portable fuel tank etc) see if it still has the problem. Then work back to the carb through the fuel lines. If you isolate it to the tank, drain and clean the tank, fuel pickup (screen, anti-siphon check valve) then check/replace the filter, fuel pump etc.

If it's ignition related, since there's really nothing wrong with points systems, it could be a poor connection anyplace or a corroded battery connection, ground, etc.


Regards,


Rick

 

[fmizell@95842]

Re: 1987 OMC 3.0 jerks or stalls for a split second when cruising at 3000 rpm

Had Carb rebuilt and ran @ lake with same results. Engine is not starving for fuel but problem seems like outdrive wants to jerk and shift out of gear for a split second..Thinking now this could be a problem with ESA or the Dog clutch in lower unit or possible cable adjustment..


I think you should determine the cause before you start replacing systems.

If the engine appears to quit/starve, etc regularly, it could be fuel related. If fuel tank vent line is partially plugged, it will restrict fuel flow and possibly cause what's happening.

Try running the engine on a different fuel source. (portable fuel tank etc) see if it still has the problem. Then work back to the carb through the fuel lines. If you isolate it to the tank, drain and clean the tank, fuel pickup (screen, anti-siphon check valve) then check/replace the filter, fuel pump etc.

If it's ignition related, since there's really nothing wrong with points systems, it could be a poor connection anyplace or a corroded battery connection, ground, etc.


Regards,


Rick[/QUOTE]

 

[HT32BSX115]

Re: 1987 OMC 3.0 jerks or stalls for a split second when cruising at 3000 rpm

Had Carb rebuilt and ran @ lake with same results. Engine is not starving for fuel but problem seems like outdrive wants to jerk and shift out of gear for a split second..Thinking now this could be a problem with ESA or the Dog clutch in lower unit or possible cable adjustment..

If it's jumping out of gear, that is a totally different problem altogether.

If your lower shift cable is defective/out of adjustment, it's possible that the damage is already done (to the shift dogs)

If the ESA is activating, it doesn't completely "kill" the engine but it does cause the ignition to pulse.

Sounds like you might need to carefully inspect the entire shift system. If you need to replace the shift cable, make sure you get the correct OEM service manual.

Also, have a look at the following info.

OMC Cobra Sterndrive Tech Info

 

[MikDee]

Re: 1987 OMC 3.0 jerks or stalls for a split second when cruising at 3000 rpm

If it appears to be like an electrical switch going on, and off, (almost like a short in the wiring) then I would say corroded connections cutting off the power momentarily. Unless it's a new boat, take off your battery cables, and possibly starter connections, and clean them up real good, then put them together with some dielectric grease.

 

[fmizell@95842]

My problem turned out to be the dog clutches in the lower outdrive. I found one out of a 1986 w/v8 and large gearcase. I used my upper joined with the larger lower..problem solved...runs out fine so far..

 

[jerryjerry05]

Good for you.
Thanks for the update.
No problem with the lower being bigger?
Slow you down?

 

[fmizell@95842]

No problem except I have to use different props with a 15 spline instead of the 13 spline on my original lower..There is a slight difference in the overall ratio now but changing to a lower pitched prop compensates for this..