OMC Cobra stalling when shifting into reverse.

[Ck111484]

Drive is a '93 OMC Cobra mated to a Ford 302 (5.0) HO.

NOTE: I HAVE THE DRIVE WIRED LIKE A MERCRUISER BECAUSE MY ESA MODULE DOESN'T SEEM TO BE WORKING.

My boat shifts fine into forward and comes out of gear into neutral fine, but about 75% of the time when going INTO reverse, it will stall immediately. Since I have it wired like a Merc, it dies instantly, and unhooking the interrupter switch solves the problem, I know that the problem is that the interrupter switch is being held too long while the drive is shifted into reverse (and it shouldn't even be activated at all going INTO gear).

I installed a brand new lower shift cable about 6 weeks ago, measured very carefully, and everything seems to be adjusted correctly (ie. the control box hits reverse and forward evenly, neutral is directly centered, full throttle puts the lever straight forward, etc.).

What can I check/adjust/replace to stop the interrupter switch from being activated while shifting into gear?
I'm beginning to understand the system more and more, but if you could use laymans terms I'd greatly appreciate it.

Any input is appreciated,
Thanks.

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

Howdy,

(and it shouldn't even be activated at all going INTO gear).

You have it totally "pegged"!!


If it's being activated going into either FWD or REV, either the force required to move the lower shift cable into gear is too high (something is binding)
or the "Shift Interrupter Spring" for the shift actuator is too weak.

I read somewhere that OMC had a problem with some of the shift interrupter springs being too weak on some models. I don't know which models or years though.... A weak spring would allow the actuator to move too far (and activate the switch) when going into gear.

You're in unknown territory though using the system like a Mercruiser. I have heard of people doing this but I suspect that OMC had the ESA for a reason. They would have DEFINITELY eliminated it if they could have since it would have saved a LOT in final cost of the system.

 

[Ck111484]

Re: OMC Cobra stalling when shifting into reverse.

Thanks for the reply.
I know I'm in unknown territory with the wiring... I recently replaced the ESA module with a new CDI unit, and was able to get it working, but I switched it back to the Mercruiser wiring because I was having issues with the engine stalling while shifting (which I now believe was due to a clogged carb + the ESA activating when it shouldn't); now when I re-connect the ESA it doesn't appear to be working anymore. I need to troubleshoot the wiring, just haven't had time.
I definitely plan on getting the ESA functioning; the Merc wiring is just a temporary "band-aid" so that I can use the boat and won't damage the gears.

Regardless though, I know the interrupter switch shouldn't be activating while going into gear, so I'd like to figure that out.
I will check out the interrupter spring. Like I said, everything else seems to be in fine working order; I wonder if the spring can lose strength over time?

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

I wonder if the spring can lose strength over time?

I doubt it.

But if the drive was requiring a little more force to shift into and out of gear,
the (always) weak spring might allow the shift actuator to move when it it shouldn't.

 

[Ck111484]

Re: OMC Cobra stalling when shifting into reverse.

Just ordered a new spring... we'll see if it makes any difference.

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

Another thing to consider might be what you're using for oil in the drive. I stopped commenting on "whose" oil it is (brand) in the drive.

Several years ago I switched to a synthetic oil in my manual transmission car.

It the winter time when it was REALLY cold (5F or so) It took a fair amount of effort to shift the transmission until it warmed up.

When I switched to synthetic gear lubricant, it made a huge difference in ease of shifting when the transmission was cold soaked.

Mercruiser now suggests people use their own synthetic gear oil (as does Volvo I think)

If you're not using Mercury HP, Volvo, or OMC/BRP/Evinrude or other (SYN) marine gear lubricant, you might give it a try.

It *may* reduce the forces required to shift the drive into gear enough to keep the actuator from actuating the switches. (I'd replace the spring just the same too.......)

Just a thought..........


Rick

 

[Ck111484]

Re: OMC Cobra stalling when shifting into reverse.

A quick update: I rigged up a switch to the ground side of the coil... basically I can turn the interrupter switch on and off. The way I have it wired is so that it's acting like a kill switch (Mercruiser style).
When IN gear in reverse (ie. backing up), if I activate the switch, it kills the ignition. In other words, the interrupter switch is being pressed the whole time the drive is in reverse, not just when shifting. This surprised me.
Any ideas?

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

I'm not sure I'm following you. The way the shift actuator is designed, (assuming the cables and linkages are adjusted correctly,) the shift actuator will only move one way or another is when you move the "shifter".

When it actually IS in gear, (FWD or REV), The shift actuator *should* be centered, (and neither switch activated)

 

[Ck111484]

Re: OMC Cobra stalling when shifting into reverse.

Hmm, well the interrupter switch is definitely activated while I'm IN reverse because when I activate it (with the dashboard switch I installed), the engine cuts out. I guess the shift actuator must not be centered then. I'll have to check.
Would that be a cable adjustment or can I adjust the actuator itself?

I'm always troubleshooting this stuff by myself, so I haven't had the chance to have anyone watch the mechanisms while I shift.

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

Hmm, well the interrupter switch is definitely activated while I'm IN reverse because when I activate it (with the dashboard switch I installed), the engine cuts out. I guess the shift actuator must not be centered then. I'll have to check.
Would that be a cable adjustment or can I adjust the actuator itself?

I'm always troubleshooting this stuff by myself, so I haven't had the chance to have anyone watch the mechanisms while I shift.

If you look at how the actuator does it's job, there's a slight "lever" action when you place the drive into or out of gear.

With the engine running, the forces required to move into and out of gear are the same WHEN THE PROP IS UNLOADED. (I.E. out of the water)

When you put the boat in the water, the force to go into gear doesn't change.......but the force required to get it out of gear is increased greatly due to the under-cut clutch-"dogs" being held together by the torque applied to turn the prop in the water.

You want that force increased (to come out of gear) so the shift actuator will move up against it's respective micro-switch (FWD, REV) and the ESA activate to pulse the ignition and give you the torque (reduction) pulses necessary to allow you to pull the clutch-dogs apart.

You do not want it to be easy to pull those clutch dogs apart. OMC originally thought the amount of under-cut was insufficient so they increased it a bit. When they discovered that the undercut wasn't the problem, they quit doing that. This is all info from http://www.hastings.org/~stuart/cobra/

You might read all the stuff there and the references. There's a lot of good background info.....

If your Shift-Actuator is still fully "actuated" when you're in gear, it's most likely a lower shift cable adjustment problem because even if the actuator moves when you go into gear it should "snap" back to center immediately....

If the force required to go into gear is "about right" the actuator shouldn't move far enough to actuate the switches anyway.

 

[Ck111484]

Re: OMC Cobra stalling when shifting into reverse.

Thanks a lot for the info, appreciate it!

It's interesting, because I made very sure that my lower shift cable measurements were accurate, or at least I thought I did; ie. bellcrank @ 90 degrees, 7 9/16" (IIRC) at the engine end, etc.; and like I said the control box seems perfectly aligned, so I'm not sure what's going on. I'll have to take a good look at it with someone else shifting. I imagine it is "snapping back" into alignment when I go into forward, just not reverse.

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

I'll have to take a good look at it with someone else shifting. I imagine it is "snapping back" into alignment when I go into forward, just not reverse.

That's the key here.......You need to have someone shift it for you while you watch the shift actuator. The actuator should immediately center (if it moves at all going into gear) after you get it in gear.

If there's still enough force (on the lower shift cable) to keep the actuator positioned in one direction or the other (NOT centered)............ the lower shift cable is NOT adjusted correctly.

 

[Ck111484]

Re: OMC Cobra stalling when shifting into reverse.

So if the actuator doesn't center itself, which part of the lower shift cable is likely to be incorrectly adjusted?
Like I said, I measured things out quite carefully when installing the new cable, and everything worked as it should afterwards, but this problem seems to have developed over a few weeks.
I guess what I'm asking is, as long as everything was measured correctly and the bellcrank was at 90 degrees, what else is there to adjust?

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

I guess I am "mixing" both cables into the discussion here.....

Imagine you are pushing the UPPER shift cable yourself by "hand" (which you essentially are with the "shifter") .

If you always push it just a tad too far, (that is, slightly farther than it takes to get the drive into gear) the "upper" shift cable movement will continue to place pressure on the shift actuator (because of the slight offset in the mechanism).



Let me say it a different way (my wife says I repeat myself!!!)

The drive is full "in-gear"

If the upper cable connected to your shift quadrant still moves a little after the drive is in gear......... the actuator then moves because the lower shift cable cannot move any further. (AND the upper cable will not move any further if the shift actuator "bottoms-out" in either gear.


So your LOWER shift cable could be adjusted just right.

But if you the "upper" cable continues moving after the lower one STOPS moving (i.E. the drive is IN-gear) then the actuator will "take up the slack" until it hits it's "STOP" (AND/OR actuates one of the switches)


Does that make sense?

 

[Howard Sterndrive]

Re: OMC Cobra stalling when shifting into reverse.

OMC's ESA system is designed to assist going in to gear as well as shifting out of gear. Unlike Merc's interrupt system which is designed to only assist coming out of gear.
Why not just replace the module? $105, bolt it on and go.

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

OMC's ESA system is designed to assist going in to gear as well as shifting out of gear. Unlike Merc's interrupt system which is designed to only assist coming out of gear.
Why not just replace the module? $105, bolt it on and go.

I think I might disagree with that. There's no assistance needed going into gear with any dog-clutch and pulsing or stumbling the engine doesn't help it going into gear. The ESA "pulses" the ignition causing the engine to "lope" to reduce the torque on the shift-dogs so they can be pulled apart. They'll engage easily as long as the idle is set right (600-650)

If it's engaging going INTO gear, the lower shift cable, or shift shaft is binding enough to cause sufficient shift actuator movement to operate the switch. It pretty much DOES work similar to the Merc system for coming out of gear (they're both using dog-clutches) except it doesn't "kill" the ignition momentarily....

 

[Howard Sterndrive]

Re: OMC Cobra stalling when shifting into reverse.

I think I might disagree with that.

ok. and I understand the theory, and realize the system is more valuable going to N
but that wasn't my opinion, it's in the OMC factory manual.
It says it operates going out of, or in to, gear.

 

[Howard Sterndrive]

Re: OMC Cobra stalling when shifting into reverse.

I read somewhere that OMC had a problem with some of the shift interrupter springs being too weak on some models.

one I am familiar with was an update for springs that were too strong.
http://www.hastings.org/~stuart/cobra/sb4034.jpg
but that's an early update (1987), a 1993 boat would have a different ESA (time-out strategy style), and a different spring again. a bit different shape to the cam. Even a different angle on the dogs in the lower unit.

For me, I'd like to know if the stalling began with the conversion to Merc-style interrupt. Or did the boat ever work really well with the Merc setup.
Whether I would continue trying to get the Merc setup to function at all depends on that.

I realize the merc way works fine on some Cobras, but there are a lot of different ESA modules with different strategies that are designed to match the corresponding linkage, clutch dogs, cable geometry, cam and springs....etc. I'm not sure the interrupt system is going to be reliable on all Cobras.

 

[HT32BSX115]

Re: OMC Cobra stalling when shifting into reverse.

Yeah. I read Hasting's discussion on too..... And quite frankly I forgot he was using an ignition interrupt [instead of the ESA] when I said that!! My 87 model never did actuate the ESA going into gear. But it ALWAYS did coming out. At the same time it doesn't need to operate either since you do not need torque reduction/pulsing going into gear. Even if it did it should never stall the engine (it doesn't [or shouldn't] and mine didn't, coming out of gear either)

I realize the merc way works fine on some Cobras, but there are a lot of different ESA modules with different strategies that are designed to match the corresponding linkage, clutch dogs, cable geometry, cam and springs....etc. I'm not sure the interrupt system is going to be reliable on all Cobras.

I am totally with you here. I think OMC would have used an IGN interrupt if they could have. But think about the way the offset cable/lever ESA system works.

If the lower shift cable or drive is just a leetle sticky, the shift actuator will move (and maybe briefly actuate the ESA) any time you shift the drive either going in OR out of gear. You don't need it going in but if it actuates briefly it really doesn't hurt anything (because the ESA doesn't kill the IGN)

If they DID use an interrupt and the above happened, it would kill the engine every time. So unless they did a complete redesign of the shift system (which would have probably cost millions $$$ to retrofit them all) they were pretty much stuck with using the ESA. which was even redesigned later to add the timer etc. Some people even think there was a rev limiter incorporated into some of them.....

Since the ESA's are still available (NEW) I wouldn't even try to use the current switch system with an interrupt unless I completely bypassed the microswitch that is actuated going INTO gear. (but that's not possible since BOTH switches are used for coming out of gear depending on which gear you're going into and out of.......REV/FWD)

You would have to have an additional set of switches on the actual shifter quadrant that bypassed or disabled the appropriate switches on the shift actuator depending on which gear you were going into.... more switches means more failure points!

Just replace the ESA!

 

[Ck111484]

Re: OMC Cobra stalling when shifting into reverse.

For me, I'd like to know if the stalling began with the conversion to Merc-style interrupt. Or did the boat ever work really well with the Merc setup.
Whether I would continue trying to get the Merc setup to function at all depends on that.

It's difficult to answer that question concisely because there are multiple variables. I'll explain as best I can.

The ESA was not functioning when I bought the boat; once I learned about the Cobra drive, I tested it at the microswitch and found it to be non-functional, so I converted the switch into a Merc-style kill switch to make the boat usable while the new ESA was in transit.

Once I received the new ESA, I wired it up (with a resistor on the power wire per CDI's instructions) and was able to make everything work; the engine stumbled coming out of gear, and did not stall going into gear (and if it stumbled going into reverse at this time I didn't notice). This only lasted perhaps one or two outings before the engine started stalling while shifting into gear. At this time, I was also dealing with a clogging carburetor, which I believe was responsible for the stalling (engine wasn't running healthy enough to keep running while in a stumble).
I returned to the Merc-style interrupt on the water to make the boat not stall, and have since fixed the carburetor issues (added a fuel filter). But now when I hook the ESA back up, it doesn't function at all (pressing the microswitch doesn't do anything), so I'm not sure whether the unit went bad, or the wiring, or what.

BUT, whether or not the ESA unit is functioning is secondary at this point because I know for sure that the microswitch is being pressed the entire time the boat is in reverse because I can turn the microswitch on and off from a toggle on the dash, and when I flip it on while in full reverse, the engine dies immediately. It shouldn't be doing this, and if the ESA was functioning properly that means the engine would be in "stumble mode" anytime the boat is in reverse, which is no good. So I need to fix whatever it is that is activating the microswitch in reverse before worrying about why the ESA module isn't working.


To review the current situation: I have the boat wired Merc-style, with a dashboard mounted toggle for the microswitch (now a "kill switch") to allow it to function or not. With it on, it works fine going into forward and back into neutral, but the engine will immediately cut out when I shift into reverse (meaning that the microswitch is being depressed and held), so I have to turn the microswitch off to get into reverse. When I turn the microswitch back on IN reverse, the engine STILL cuts out, which tells me that the switch is being depressed the whole time the boat is in reverse. So in order to get from reverse back to neutral, I have to kill the engine.
My goal is to figure out why the switch is being depressed in reverse and fixing that, THEN worry about why the ESA module isn't working.

Does that make sense?