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TOPIC: shift interrupt problem

shift interrupt problem 22 Jun 2009 21:33 #1

  • 96bayliner
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Ok guys having some problems getting the boat out of reverse. In the driveway it is fine, but out in the water I can put the shifter in nuetral but the boat is still in reverse. Did some searching and everyone seems to say that the shift interupt may be the problem. Everything I read says to bend the tab with the roller to adjust the switch. however when shifting with the hood open the part that is supposed to move over and hit the interupt doesnt move at all. I cannot seem to find a diagram or picture of how it is supposed to look with everything working correctly. I can find diagrams of how to adjust the cables, but not what actually makes that part move.

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D

shift interrupt problem 22 Jun 2009 21:47 #2

  • Glenn Dombroski
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Read a lot of posts on the shifting subject but haven't hit one that matches your problem. But, I know bending it is not recommended. It rocks as a result of the cables moving and when they are adjusted properly should always center itself. If you move the throttle you should see its movement.

Anyway that's not your problem as to my knowlege the ESA has nothing to do with getting in or out of gear properly except for reducing RPM during shifting so it doesn't eat up the gears.

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1989 Bayliner 2955 Avanti with Twin 5.8L

shift interrupt problem 22 Jun 2009 22:04 #3

  • captjmh
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If I understand the problem - you can shift the shift lever into neutral but the drive stays in reverse. That would not be an ESA issue. When the ESA module or Cherry switchs fail, you will not be able to get the shift lever to move out of gear.

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shift interrupt problem 22 Jun 2009 22:07 #4

  • 96bayliner
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from what I have read the shift interupt is just supposed to momentarily drop the rpms on the boat to take the load off the gears long enough to get it in neutral. Apparantly you should hear the motor drop rpms for a split second when shifting out of gear and mine doesn't. Figured I would start there as I know that something is wrong with it before moving on to adjusting the cables.

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D

shift interrupt problem 22 Jun 2009 22:10 #5

  • 96bayliner
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captjmh; you are correct in what the problem is. However like I said I do know for sure that the switch isnt working correctly.

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D

shift interrupt problem 22 Jun 2009 22:12 #6

  • spike2450
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Hi

I've had issues this year, i've adjusted her best i can as i believe i need new shift cables.
My switch will only move when the boat is afloat and with the extra drag from the water.

Here's a post i got from another site that explains the switch in detail.

Here is something that may help troubleshoot.
Note particularly point #6.

Shift Interrupt Switch Problems (Not applicable to Bravo drive units)

NOTE: The interrupt switch is located on a cast bracket where the shift cable from the throttle quadrant attaches. It is usually mounted at the rear of the engine on the upper exhaust elbow, or a bracket on the valve cover. The front cable is the upper one, and the lower cable runs from the bracket out behind the exhaust down pipe, and to the transom plate assembly.

1. The shift interrupt switch (aka “Kill” switch) is a normally open switch for carb applications. It’s roller (or plunger) normally sits centered in a “V” shaped notch in the actuating arm of the shift cable bracket assembly. The arm tends to stay centered due to a fairly stiff centering spring.

2. Normally, whenever the shift lever is moved from Fwd or Rev gear into neutral, there is a brief moment when the lower shift cable meets resistance. This is caused by the tendency of the rotating prop dog clutches to stay engaged when the prop is turning in water. This resistance overcomes the centering spring, and the switch roller rides out of the V notch and CLOSES the switch.

3. The closing of the switch then shorts out the points (or the Thunderbolt ignition module) and kills the engine’s spark. The engine momentarily dies and this small interruption allows the gear dog clutches to disengage.

4. Once the gears are disengaged, the resistance in the shift cable is relieved, and the centering spring returns the switch roller to the V notch. Spark resumes and the engine picks up to normal idle speed once again. This whole sequence happens in a fraction of a second, and is barely noticed by the operator.

5. Whenever the shifter is in neutral, Fwd, or Rev, the switch roller must be centered in the V notch. If it’s not, the switch will be closed and there will be no spark. The engine will not start or run, though it will still crank over.
The position of the switch should be checked first if there is no spark. Also check the switch and wiring with an ohmmeter to make sure it is not shorted out even when the roller is in the V notch.

6. If the interrupt switch is not killing the ignition properly it will be very difficult to shift the drive out of gear, when the boat is in water. (It may still seem to shift fine during a driveway test, with no water resistance.) You can check the switch operation by manually depressing the switch roller with the engine idling. If the switch is working, the engine should die immediately. If it does not die, either the switch is not closing, or the wiring is faulty.


7. If the engine inexplicably dies when shifting into gear, or while accelerating or decelerating, the interrupt switch may be the cause. If the shift cables are out of adjustment, or if the lower shift cable is damaged or stiff (or the drive leg shift mechanism is stiff), this will put extra load on the actuator arm (sufficient to overcome the centering spring) and the switch will close, thus killing the engine.

8. To resolve this situation first make sure the shift cables are adjusted correctly per instructions. If this does not resolve the issue, disconnect the upper shift cable eye, and manually move the lower shift cable lever back and forth to push the lower cable in and out. It should move freely from stop to stop without binding or tight spots or excessive effort. One finger should do it easily. If binding or sticky such that the switch V notch arm visibly moves, the cable likely needs replacing, or the shift lever mechanism in the drive leg needs servicing.

9. Since replacing the lower shift cable with the engine in place is a rather ugly job, first remove the drive leg and recheck the cable operation. The problem may be in the drive leg shift shaft mechanism, or the upper shift shaft arm, or the roller and slider mechanism. Make sure these all operate freely, then re-install the drive leg and retest the lower shift cable.

10. One caution: On EFI engines the interrupt switch is a normally closed type. This type of switch has a gray body and an actuator pin that sits in the V notch, instead of a roller. Thus when the switch pin rides out of the V notch, the circuit OPENS. This action then kills the ECM controlled spark.

11. This means that for EFI engines the interrupt switch needs to complete the circuit for there to be spark. If there is no spark, check to see if the switch pin is in the V notch, and that the switch circuit has continuity. Otherwise the theory of operation is the same as for carb engines.

12. One further note: Your installation may include a so-called “shift assist” assembly. This is essentially a spring-loaded centering device that connects to the same pin as the upper shift cable end. It has a black plastic body that is about ¾” diameter X 9” long, and sits right alongside the upper cable sleeve. The spring tries to return the shift lever to neutral from either Fwd or Rev, and it’s sole purpose is to reduce the effort required to shift out of gear. Shifting will work fine without the shift assist; it will just take somewhat more effort to return to neutral. Merc recommends that the shift assist only be used with single lever throttle quadrants.


Make sure that if you make any adjustments to the linkages that you write down what turns etc you make so that you can go back to your base setting and not chase the error. :hammer

Good luck

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1998 2452. 5.0l mercruiser with alpha one gen 2 and 2 bbl :)

shift interrupt problem 22 Jun 2009 22:19 #7

  • spike2450
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Another quick thought is to make sure your idle isn't to high.

I've read on other forums when other boaters have there idle really low and don't bother with the switch.

Here's that site. www.marineengine.com go into there discussion board.

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1998 2452. 5.0l mercruiser with alpha one gen 2 and 2 bbl :)

shift interrupt problem 22 Jun 2009 22:36 #8

  • captjmh
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96bayliner;313437 wrote: captjmh; you are correct in what the problem is. However like I said I do know for sure that the switch isnt working correctly.


From the following post from spike2450, you have a pretty thorough explanation of the problem and fixes. If you know the switch is not working by manually activating it like noted below, sometimes you can revive the switch with a healthy shot of WD40, but the better long term solution is to order new switches - they are not expensive and easy to replace. I seem to recall about $12 ea.

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shift interrupt problem 22 Jun 2009 23:07 #9

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No actually the switch is ok, if you manually push it the motor reacts. However the part of the linkage that it rides against isnt making it move.

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D

shift interrupt problem 22 Jun 2009 23:28 #10

  • spike2450
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Hi
Has any maintenance been done on the boat since it was last working ok?

Due to adjustment problems (read my other posts) i've had to remove my shift assist and sometimes when i take it out of forward gear and it feels from the remote that i'm in neutral - but i will still be in gear, i will then have to rock the remote slightly untill she comes out of gear.
I believe it could be a worn shift cable, if it's stretching to much then the cable won't feel that split second resistance from the dog clutch ( in the water) and therefore not operate the switch.

Try No 8 above and see if you are getting a nice smooth movement, boat out of water assistant turning prop (without engine running) and see if she is going fully into each gear etc. (worth marking the inner stainless sleeve with a marker pen when in both gears for reference later if adjusting mechanism).

I made the mistake of chasing the error, an experienced Mercruiser could adjust it in minutes.

Good luck

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1998 2452. 5.0l mercruiser with alpha one gen 2 and 2 bbl :)

shift interrupt problem 23 Jun 2009 00:11 #11

  • JohnL
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spike2450;313444 wrote: Another quick thought is to make sure your idle isn't to high.

I've read on other forums when other boaters have there idle really low and don't bother with the switch.

Here's that site. www.marineengine.com go into there discussion board.


I've looked in their archives back a year and can't find anything. Can you point to a specific place?

I'm having problems with mine and wondering if that is an acceptable temporary alternative to shift cable replacement.

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Blue Highways
93 2452

shift interrupt problem 23 Jun 2009 00:24 #12

  • Merlin
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Hi Bayliner96,

Any backlash in the shift cables needs to be removed from the system. Both remote control lever cables and driveleg shift cable. This is all done with a sequence of adjustments at the shift bracket mechanism where the shift interrupt switch is. OEM and other workshop manuals should have details on these adjustments. I'm familiar with the adjustments for a Cobra drive but they may be slightly different for the Alpha drive and I wouldn't want to give you bad information.

As a side note, OMC supplied a modified shift bracket actuator spring that keeps the 'V' cam centered. It had less tension in it, so allowed the cam to move with less force applied to it by the shift cables. This wouldn't be a cure for mal-adjusted shift cables though.

Some info on the Cobra adjustments can be found in here - http://www.hastings.org/~stuart/cobra/kwshift2.jpg - It might give you some idea of what's trying to be achieved, or what to look for in the manuals.

Hope it's of some help>

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Ian S.
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YOUR WORST ENEMY!!! ;) :D

shift interrupt problem 23 Jun 2009 02:20 #13

  • MikeValent
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The thread's a little confusing with some references to an "ESA" but this problem is apparently with a Merc Alpha, not an OMC.

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shift interrupt problem 23 Jun 2009 11:25 #14

  • Merlin
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Yes Mike I understand it's a Merc Alpha.

The principle of removing backlash from the cables is similar tho! With the same end result, to improve sloppy shifting! I gave that link to give the guy an idea of what he's trying to achieve to improve his situation. I know Mercruiser may have a different sequence of adjustments, but it was only to give an idea of the terms used in shop manuals for the adjustment procedure. Unless someone can come on here and give this guy step by step instructions on how to adjust his particular setup any information is better than none! It's a reference point to start from when looking in a Mercruiser manual for the Mercruiser adjustment application.

I did state in my post that:

[It might give you some idea of what's trying to be achieved, or what to look for in the manuals./QUOTE]

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Ian S.
'89 5.0L Merc LX/OMC Cobra (Don't Ask! Please!!)
'88 Trophy HardTop (Dunno Model Tho!)
6 YEARS BOATING, AND STILL LEARNING!!
AN OLD BOAT IS THE BEST THING TO GET
YOUR WORST ENEMY!!! ;) :D

shift interrupt problem 23 Jun 2009 13:54 #15

  • SwampNut
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I've screwed around a lot with issues like this over the years. Two things I've learned are that even slightly stiff cables will create a lot of hassles, and that there is a whole new shift plate/interrupt assembly that is vastly better than the old one. The new shift plate assembly is clearly better designed and less likely to have problems in the future. This is where I'd start considering your symptoms.

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shift interrupt problem 23 Jun 2009 17:28 #16

  • spike2450
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Hi JohnL

here's that link:

http://www.marineengine.com/discus/messages/12486/84355.shtml

Peterchamberlains entry

Regards

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1998 2452. 5.0l mercruiser with alpha one gen 2 and 2 bbl :)

shift interrupt problem 23 Jun 2009 17:55 #17

  • JohnL
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spike2450;313787 wrote: Hi JohnL

here's that link:

http://www.marineengine.com/discus/messages/12486/84355.shtml

Peterchamberlains entry

Regards


Thanks, Spike. He might be correct on that, but a couple of later posts in the thread warned that damage could result from disconnecting the switch so I decided not to try it. Thanks again.

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Blue Highways
93 2452

shift interrupt problem 23 Jun 2009 22:11 #18

  • 96bayliner
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alright now I am really confused. with the engine running in the driveway, that bracket that is supposed to trigger the switch doesnt move at all. However with engine off it seems to move like it is supposed to. ????

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D

shift interrupt problem 24 Jun 2009 00:00 #19

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96bayliner;313890 wrote: alright now I am really confused. with the engine running in the driveway, that bracket that is supposed to trigger the switch doesnt move at all. However with engine off it seems to move like it is supposed to. ????


The cam that triggers the cutout switch only moves when you are shifting OUT of gear, and then it is based on the resistance of the engaged gear to disengage. There may not be enough force on the gears in the driveway without water resistance to make it move.

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Blue Highways
93 2452

shift interrupt problem 24 Jun 2009 00:21 #20

  • 96bayliner
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yeah i realize it is only for shifting out of gear. However I would think there would be less load when the engine is off than when on. And it works with engine off and doesnt with it on.

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Nick
1996 2050 cz
4.3L alpha 1...looking for a 350:D

shift interrupt problem 24 Jun 2009 01:59 #21

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However I would think there would be less load when the engine is off than when on.

When the engine is not running, the gears can lock into place and make it impossible to shift.

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shift interrupt problem 24 Jun 2009 20:23 #22

  • spike2450
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Hi
When the engine is not running you will need an assistant at the back of the boat spinning the prop for it to fully lock into gear. You'll probably find the the switch will then act the same.

If you download the mercruiser manual from the library for the adjustment procedure.

also this helped : http://www.mercstuff.com/images/shiftcable.jpg

and this: http://www.sterndrives.com/replace_alpha_shiftcable.html

and this: http://dolphinmarineservice.homestead.com//cable.html

and this : http://www.sterndrives.com/merc/mdtips02.html

Disconnect the remote cable and make sure that the lever is moving smoothly from full fwd to reverse Gear, while an assistant turns the prop (engine not running).

There must be a reason for the failure, has the outdrive been removed etc.
Regards

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1998 2452. 5.0l mercruiser with alpha one gen 2 and 2 bbl :)
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