stalling while shifting to drive

here is my situation. WHen I shift to drive the motor dies if i shift slowly. if i shift fast it doesnt stall. SHifting in reverse there is no problem all is good. can anyone suggest anything to me. I am new to boat repair. 1989 omc cobra

Both the OMC Cobra and Mercruiser A drive use Dog Clutch gear engagement.
Many outboards also use this type of gear engagement.

Going into gear is usually never an issue, it's coming from gear into Neutral that is the issue.
This is because of the Dog Clutch teeth inclined or ramped areas that hold them engaged once a load is placed on them.
This is part of the design.

Here's a Merc sliding sleeve.... very similar to the OMC Cobra.
While difficult to see in the image, the actual contact areas are inclined or ramped.... they are not straight or 90*!



Here are two of the corresponding speed gears and dog clutch inclined or ramped engagement teeth.
(the center gear is the "drive" gear.... or aka "pinion" gear by some people)




Example only in this next image:
Here we have the two "driven" gears (FWD and REV)
The "drive" gear is not shown.
What they're calling a "clutch dog" I'm calling a "sliding sleeve".
The sliding sleeve installs onto the prop shaft splines (splines are not visible in this image).

All hypoid gear teeth are continuously engaged with one another, and will be turning whenever the engine is running!
The sleeve is free to be moved in either direction for either gear selection.
Only the Dog Clutch teeth actually transfer power to the prop shaft when engaged with either the FWD or REV gear.




When in gear, and at low engine speed, and with the prop in the water, the prop thrust resistance places a light load on these engagement teeth.
Again... this is by design.
In order to over-come this load, we must momentarily lower engine RPM.
This is accomplished via the OMC ESA..... (electric shift assist).
Merc's system is a SA (shift assist).

The lower shift cable resistance moves/operates a cam lever that operates a micro switch during a change from IN GEAR to NEUTRAL.
The micro-switch (and it's circuitry) momentarily inhibits the ignition system.
During this quick ignition "stall", RPM is lowered, the Dog Clutch teeth pressure is reduced, and a shift can be completed simultaneously.
Once the shift is complete, engine RPM return to normal.

Your shift into and out of gear should be crisp, concise and with no hesitation.
If not, the engine may stall out and die.
It is also possible that the system is out of adjustment.
Or... the lower shift cable has become worn and is stiff.

What ever you do, or whoever you have correct and/or adjust this, the final testing must be performed in the water.
We cannot simulate the prop thrust unless the boat is in the water.

Good luck!

Here is the best written article on adjustment of your drive.
SHIFT SYSTEM ADJUSTMENTS for "KW-RG" (1986-1991) CLUTCH DOG MODELS

I had same problem, on the shift linkage attached to intake manifold is a electric switch that retards the timing to slow rpm's while shifting. If you shift slowly it will cause a stall and can chew up your gears. OMC recommends quick firm shifts to avoid this. But this switch can need adjustment or just plain old get stuck and cause a stall. I would start there and just play with it while boat is running. Mine needed minor adjustment and all was well

I'm not sure if the ESA system actually retards timing, but rather interrupts the ignition as to cause a momentary RPM drop.
This is when gear disengagement occurs, and the ignition is immediately restored after disengagement is completed...... if all is working correctly.


The Stuart Hastings site is a good one. Stuart has spent countless hours putting his web site together.
If the ESA and lower shift cable adjustment procedure does not work for you, there is an alternate method that works well also.
If anyone is interested, I can find it and post it.

.

Hi, I've got a 1988 cobra and had exactly the same problem, the wrong idle speed along with a sticking ESA was the problem. If you locate the gear cable where it attaches to the engine you'll see a rocker/cam with a "V" notch in the middle as you change gear the switch arm moves out of the V so switching the ESA on. When changing slowly the switch sometimes fails to return to the V and leaves the ESA on. With mine a good few squirt of penetrating spray loosened everything back up. No more stalling.

Rick, seem to be depending on you for lots of info today but as I intend to check/replace the lower cable as part of my overhaul, details of the alternate setting method would be great.

What stuart does if followed exactly. will give you a complete good running drive.
See you make sure every facet is in specs. But i agree i have seen the little screw that connects the micro switch be a little to tight and will bind the switch.
I also have seen the esa module removed and the engine wired like a merc. Unplug both the overstroke and esa micro's and one wire from the micro that operates the esa goes to a ground the other wire to the neg. side of the coil and wola no more esa module. But the micro has to be good in ether case.