1989 5.7 cobra shift interrupter

[Donzi GT250]

I noticed that when shifting out of gear on my 1989 5.7 cobra the V notch cam doesn't move far enough up or down to engage the shift interrupter switch and yes the boat is in the water so there is a normal water load on the prop.
The V notch cam moves some while shifting but not far enough for the roller on the interrupter micro switch to cause the RPM to drop.
If I trip the switch manually it works as it should and interrupts the RPM's for 5+ seconds as long as I hold the switch in the activated position.
I also have the newer style shift module which bypasses the two front over-stroke switches.
It seems that during shifting there isn't enough tension being placed on the interrupter switch cam (by the transom shift cable) to move it far enough to engage the interrupter switch in either direction.
Should the interrupter cam always move far enough to engage the interrupter switch during every shift out of gear or only if the shift tension is high enough to move the interrupter switch cam ?

I just had my drive rebuilt and the company that rebuilt the drive hones the internal shift detent lever in the lower drive case to lessen the amount of force needed to move the vertical outdrive shift lever. So maybe the shift lever movement is so smooth and easy to move that it doesn't create enough tension ( on the transom shift cable) to move the interrupter switch cam enough to engage the shift interrupter switch.
Also I have had a new style transom shift cable (lower cable) installed this past spring and the shift interrupter switch roller always centers in the center V notch of the cam as it should when the drive is in gear and in neutral, so I think the lower cable is adjusted properly.
Any insight into this situation as my OMC oem factory manual doesn't give specific info. about this situation would be greatly appreciated.
Thanks for taking the time to read this.

 

[Donzi GT250]

Re: 1989 5.7 cobra shift interrupter

After doing some more research I have found this. http://www.hastings.org/~stuart/cobra/sb4034.jpg
I will have to check tomorrow to see if this is the issue even though this bulletin said that this affects GDP models which are 1988 versions and mine is a 1989 350APRMED it may still have the wrong spring.

 

[indybleck]

Re: 1989 5.7 cobra shift interrupter

Thanks Donzi just put mine to bed for the winter so I'll have to check it in the spring. I don't know if mine is working or not but will check this out, I didn't use it enough this summer. This is the first OMC I've owned so a lot of this is new to me. Thanks

 

[Donzi GT250]

Re: 1989 5.7 cobra shift interrupter

Well after checking I found that my shift mech. has the correct updated spring.
And also after checking all the settings as per the OMC oem shop manual and after talking to a couple of mechanics, the only conclusion I can come up with is that my shift linkage set up is so smooth that in doesn't cause enough tension on the transom shift cable to make the shift interrupter cam to move on every shift coming out of gear.
Which according to the mechanics is a good thing and not to mess with it.
But my understanding is that with out the shift interrupter working it should be very difficult to get out of gear, which my set up isn't.
Any thoughts?

 

[HT32BSX115]

Re: 1989 5.7 cobra shift interrupter

Which according to the mechanics is a good thing and not to mess with it.
But my understanding is that with out the shift interrupter working it should be very difficult to get out of gear, which my set up isn't.
Any thoughts?

Howdy,


I am not sure that the "mechanics" fully understand why you need an ESA to begin with!

It's NOT the linkage or mechanism that prevents the clutch-dogs from being pulled apart under load. It's the undercut (3-5 degrees depending on if they were replaced or not)

OTOH, if they're SEVERELY worn out or damaged, the under cut would be less (or not-as) effective at keeping them together and it won't be long before they won't stay together at all.

It's unlikely that you have the "rare" drive that doesn't "need" an ESA.

ALL dog clutch drives need some sort of torque-interrupt ......either ignition interrupt (Merc), or the Electronic Shift Assist (OMC) to get them out of gear...... As they get easier and easier to pull out of gear they eventually won't stay in gear at all. Then you rebuild the drive.

Hastings explains the difference in the angle of the "dogs" in his excellent article.

It's possible that you have a drive with original dog-clutches (3 degree angle), that is just getting worn enough to not hold together well under load. If so, it will eventually start popping out of gear.

In that event, just run it until it "blows" and replace it with an SEI.


Regards,



Rick

 

[Donzi GT250]

Re: 1989 5.7 cobra shift interrupter

Makes sense to me but my drive has a new 5 degree cut clutch dog and new 5 degree dog gears along with all new bearings and upper gears complete rebuild.

 

[HT32BSX115]

Re: 1989 5.7 cobra shift interrupter

Makes sense to me but my drive has a new 5 degree cut clutch dog and new 5 degree dog gears along with all new bearings and upper gears complete rebuild.

If everything is new, you should not be able to easily pull the "dogs" apart while there is a (in the water) load on the prop at the correct RPM. (around 600-700) and it should be harder with the 5 degree dogs. (even though OMC eventually discovered that 3 degrees was sufficient)

If you can, either the "spring" you were talking about is in fact the wrong one or it's "defective" (too stiff)

The actual force required to pull the dogs apart with no torque interruption may eventually damage the cable.


Let me also add that if you can determine what the actual correct force required to separate (FWD/REV) them is and you're below that point (without torque interruption)

Then don't worry about it.

I find it questionable that some (Cobra dog-clutch) drives don't need some sort of torque interruption for shifting.

OMC would have saved quite a bit of money if that were the case....this is why Cone clutch drives were developed and why the new Yanmar drives don't use dog or cone clutch shifting at all (they use wet-plate clutches like an automatic trans instead)