Shift Problem on 1991 OMC Cobra 5.0L H/O

[domingum]

My Cobra shifts smoothly into forward and runs fine. However, when I shift it into reverse it seems to bog as the gear engages, then stalls when I apply throttle. When I disengage the drive (by pushing the center button on the shift lever) the engine throttles smoothly in both forward and reverse directions. Was wondering if anyone had any ideas? I was thinking it might be a shift interrupter switch problem where it doesn't disengage and return the engine to normal unretarded operation once in reverse...any thoughts?

Took the boat to the shop and mechanic said he adjusted the shift cable and now the boat runs like new...however, when I put the boat in the water it exhibited the same symptoms with exception of a couple of times that the engine did not stall (those times I shifted into reverse just enough to engage the drive then let it idle back, then slowly applied a little throttle and the engine didn't stall...amazing).

Getting frustrated and hope someone can tell me something I can tell the mechanic to put him on the right track.

 

[domingum]

Re: Shift Problem on 1991 OMC Cobra 5.0L H/O

Didn't get any replies the first time so I thought I'd try to resubmit.

 

[Gary H NC]

Re: Shift Problem on 1991 OMC Cobra 5.0L H/O

What is the idle rpms in gear? Should be around 600.
When you pull it back to go into reverse does it idle up before engaging?
Its should just be a quick motion going into gear with a slight clunk.
The shift interupt is only supposed to kick in when coming out of gear.

 

[HT32BSX115]

Re: Shift Problem on 1991 OMC Cobra 5.0L H/O

My guess is that the shop did not know how to do the job.


It's not possible to test the lower cable shiift adjustment reliably when out of the water.(It will ALWAYS come out of gear easily on the trailer)

1. Do you have a (correct) service manual?

2. have you read this

The shift bracket linkage will NOT (and SHOULD NOT) activate the ESA if the drive system in NOT loaded.

The drive is only (torque) loaded when in gear and IN the water. When loaded it takes a considerable force on the main and lower shift cables to get it OUT of gear when the engine is running.....So OMC devised a clever "lever" system that when a certain amount of force in either direction is applied to the lower shift cable. A series of micro switches are activated by a device (#37 in the lower picture below) which activates the ESA (#62) This causes the engine to "stumble" which produces a torque interruption or reduction as it were that allows the amount of force you applied to the cable to NOW be enough to get it out of gear. If the switches DO NOT activate the ESA it will take CONSIDERABLE MORE force to get it out of gear (which could be enough to damage the cables or linkage)

The Hastings article explains it in greater detail.

Bottom line, If the lower shift cable or any of those switches are even slightly out of adjustment(or defective) the ESA will either not work when it's supposed to or will activate when you don't want it to.

Like Gary said. It's ONLY supposed to work when coming out of gear.

(AND ONLY when you have "coming out of gear pressure" on the control....AND that ONLY happens in the water!!)



Cheers,


Rick

 

[domingum]

Re: Shift Problem on 1991 OMC Cobra 5.0L H/O

Thanks for the replies Gary & Chief...

Idle speed is around 600 rpm. When I shift into reverse (when the boat is in the water), I hear/feel the the idle up and clunk as it goes into gear. However, if I add any throttle after in reverse, the engine seems to bog badly and most often stalls (not a good thing when maneuvering or coming into dock, as you can imagine).

I had the boat in the water again this weekend and noticed that by the end of the day the bogging and stalling wasn't as bad as in the beginning of the day. In fact, if I shifted into reverse but didn't apply any more throttle for 10-15 seconds, then slowly applied reverse throttle, the engine didn't seem to bog or stall...strange.

I have absolutely no problem going into forward nor coming out of either forward or reverse...and no problem throttling up the engine in reverse if I have the drive disengaged at the throttle handle (by pushing in the center button).

Chief, thanks for the article and for the drawing. I had seen the article, but not the drawing.

Any other ideas?
Mark