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Shift Interrupt Switch for 1988 3.7l...

Discussion Forum at MarineEngine.com » Mercruiser Sterndrive » Shift Interrupt Switch for 1988 3.7lx Merc. 180hp « Previous Next »

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Thomas McGee
Member
Username: 1973browning

Post Number: 52
Registered: 01-2009
Posted on Sunday, January 24, 2010 - 06:09 pm:   Edit Post Delete Post View Post/Check IP

Need to know if I can run a wire off of key switch to Shift Interrupt and then take wire to coil somehow? I started from scratch with wiring and do not have a factory harness so I basically need to know what the two sources hook up to and how does it cut off the ignition system. I am guessing it has to be through keyswitch,remote control and the ignition coil somehow? Any help would be appreciated! thanks, Tom
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Bt Doctur
Senior Member
Username: bt_doctur

Post Number: 1277
Registered: 06-2006
Posted on Sunday, January 24, 2010 - 06:23 pm:   Edit Post Delete Post View Post/Check IP

Depends of the ign.
electronic usually needs 12+ to cause the miss, points need a ground to cause the miss.
miss= stumble
http://www.marinepartsexpress.com/merc_sch_fs.html
shows points system for that year.
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Kghost
Senior Member
Username: kghost

Post Number: 1203
Registered: 07-2008


Posted on Sunday, January 24, 2010 - 06:26 pm:   Edit Post Delete Post View Post/Check IP

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Kghost
Senior Member
Username: kghost

Post Number: 1204
Registered: 07-2008


Posted on Sunday, January 24, 2010 - 06:27 pm:   Edit Post Delete Post View Post/Check IP

Both tap off the negetive side. I looked at the manual for both. In essence they short out the output to ign and tach.
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Kghost
Senior Member
Username: kghost

Post Number: 1207
Registered: 07-2008


Posted on Sunday, January 24, 2010 - 06:37 pm:   Edit Post Delete Post View Post/Check IP

Your stock ignition is a point ignition so the shift interuptor wires

one goes to ground and the other goes to the Negitive - side of the coil. It does not matter what wire from the switch goes to what as long as one goes to ground and the other goes to the - side of coil.
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Thomas McGee
Member
Username: 1973browning

Post Number: 53
Registered: 01-2009
Posted on Sunday, January 24, 2010 - 11:15 pm:   Edit Post Delete Post View Post/Check IP

Sorry kghost,stepped out for an hour or two. I have Pertronix electronic ignition and there are two stainless screws on interruptor switch and what you are saying is one goes to ground from interrupt switch and one goes from other pole on interrupt switch to negative side of coil. Is this correct? And thanks Bt Doctor for the help also! Thanks, Tom
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Kghost
Senior Member
Username: kghost

Post Number: 1208
Registered: 07-2008


Posted on Monday, January 25, 2010 - 06:14 am:   Edit Post Delete Post View Post/Check IP

Yes That is the case!!

My diagram is exactly the way it is set up from merc.

There should be a junction block so you can replace the switch without disrupting the wiring harness.
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Thomas McGee
Member
Username: 1973browning

Post Number: 54
Registered: 01-2009
Posted on Monday, January 25, 2010 - 05:05 pm:   Edit Post Delete Post View Post/Check IP

Alright, thats good! I am glad I do not have to splice into the ignition part of my harness. I did not think it was that simple! One last question about throw on shift interrupt switch: I do not have the drive hooked up yet but do have the shift cable hooked up to engine and respective shift shaft on bell housing and noticed that going forward with the throw on the shift interrupt linkage the shift interrupt seems to activate nicely, but when you push toward the stern with linkage nothing happens unless someone were to hold against end of shift cable from bellhousing side. Question: Is this because when the stern drive is hooked up there is only so much travel and then it bottoms out making the other throw on shift interrupt function properly? I figure that is the case but am not sure. When my brother held resistance as I moved linkage toward stern it seemed to function properly. Also, I am assuming that all of the linkages are adjusted properly. Just want to be sure! thanks so much, Tom
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Bt Doctur
Senior Member
Username: bt_doctur

Post Number: 1278
Registered: 06-2006
Posted on Monday, January 25, 2010 - 05:35 pm:   Edit Post Delete Post View Post/Check IP

With NO EXTERNAL FORCES APPLIED ,the shift interupt should not move shifting without an outdrive.On a hose, the shift interupt should not move because there is NO LOAD on the propeller. Shift interupt ONLY WORKS when your in the water to stall the motor coming out of gear to allow the gears to come apart into neutral.
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Kghost
Senior Member
Username: kghost

Post Number: 1213
Registered: 07-2008


Posted on Monday, January 25, 2010 - 05:53 pm:   Edit Post Delete Post View Post/Check IP

Alpha 1 shift cable adjustment procedure

Raise outdrive a count of 2-3 seconds from all the way down.
Remove short cable from shift bracket at engine.
Push plastic cable end of short cable all the way IN, have someone turn by hand the prop c’clockwise until full forward engagement.
Measure distance between the center of the brass trunion to the center of the plastic cable end hole that the mounting stud went thru. This measurement must be 6 inches exactly!!

Now shift the control handle to full forward full throttle position.
Try to install short cable onto shift bracket. If it will not fit perfectly adjust the control shift cable trunion “only” until it does. Once there install short cable back onto shift bracket. Now turn control cable trunion 3-4 turns AWAY from the plastic cable end and install into shift bracket.

Shift control handle to neutral. Prop should spin freely with no clicking sounds.

Now shift back into forward but only to the “detent” aprox, 10:00 oclock . This is when forward gear should be fully engaged. Make sure someone is spinning the prop by hand c’clockwise when doing this.
If you have good forward engagement with no slipping the pull handle back to neutral.

Now shift handle to aprox, 2:00 oclock, have the person spin the prop clockwise. This should give you reverse engagement. If it does then you are done! If it does not and you have a clicking sound/ not full engagement then adjust the short shift cable end where it is mounted, there is a slot, loosen the hex nut under the cable end and move cable towards the end of the arm, say ¼ inch and retry. When full reverse is obtained you are done.
Give this a try and report back with results.

The pic below is a somewhat generic diagram. But it tells a lot of what you will be looking at.



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Thomas McGee
Member
Username: 1973browning

Post Number: 55
Registered: 01-2009
Posted on Monday, January 25, 2010 - 07:40 pm:   Edit Post Delete Post View Post/Check IP

Thats an awsome sketch! Thanks kghost and Btdoctor for the great info. I am going to have to go back to this post at a later date. Still have a ways to go on boat rebuild but I am making fairly good progress with the help of you guys. Can't thank you enough for all your help! So basically, I am not ready to do any adjustments until I am ready to install the drive onto boat. And I was not aware about the fact that interrupt will not function unless boat is in water and prop under load. So, should a person with hose hookup even be shifting outdrive in and out of gear if out of the water? (Of course with the engine at idle) thanks, Tom
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Bt Doctur
Senior Member
Username: bt_doctur

Post Number: 1279
Registered: 06-2006
Posted on Monday, January 25, 2010 - 08:03 pm:   Edit Post Delete Post View Post/Check IP

Dosent matter with the shifting on a hose,but if the shift interupt happens to be working on a hose it`s a sign of a bad lower cable or corrosion in the shift mech
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Thomas McGee
Member
Username: 1973browning

Post Number: 56
Registered: 01-2009
Posted on Tuesday, January 26, 2010 - 05:50 pm:   Edit Post Delete Post View Post/Check IP

Thanks Btdoctor, thats good to know also. I have a new shift cable and rebuilt the gimble housing and all components up to the bellhousing. I just did not get to rebuild the upper part of drive yet. Thanks again for all your help, Tom

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