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Need help adjusting my shift interrupt switch....

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Need help adjusting my shift interrupt switch....

Old 06-01-2019, 12:24 PM
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Default Need help adjusting my shift interrupt switch....

I have pulled car motors, repaired heads, diesel injector replacements, pulled my mercruiser engine and replaced coupler... YET I cannot figure out this simple shift interrupt switch. The switch works but is not engaging. The result is I can't get into neutral when the prop is under load. I made a video and uploaded to youtube. I will try to attach the link. Boat is a mercruiser 4.3 MPI.

Old 06-01-2019, 12:34 PM
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Here the adjustment in the factory manual.

Boatinfo - Mercruiser Service Manual nr. 14 - 1991-Current - Sterndrives Alpha One Gen II</
Old 06-01-2019, 12:42 PM
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It will only move the arm and depress switch when there is a load on the cable. Won't do it without motor running because there is no load trying to pull it out of gear. With motor running and you depress switch (push on arm) does it shut motor off? With motor running it should not move arm going into gear but when you try to pull it out of gear there is then a load on the cable...the arm moves and depresses the switch killing the motor for a split second allowing the gears to go into neutral.....switch resets and motor is still running.
Old 06-01-2019, 01:30 PM
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Wow good to know. It cannot be tested unless on the water. The switch does work, with engine on it cuts off when I push the switch. Perhaps my problem is fixed then because I did adjust the lever a few days ago where I think it was stuck. Have not water tested since I made this adjustment.
Old 06-01-2019, 03:40 PM
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i tried adjusting mine only to figure out it was my shift cable that need replaced.. new shift cable and it works great
Old 06-01-2019, 03:56 PM
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If this doesn't work I will try that. Just though it was too much of a coincidence that the shifting was messed up after replacing engine hub. Has to be a user error/mistake when u put back together.
Old 06-01-2019, 04:09 PM
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The switch interrupts going into or out of gear and is activated by cable tension. If the cable is too stiff it will cause stalling.
During the split second that the switch is activated it lets the engine pause so it coasts into or out of gear.
If you hesitate when shifting it won't be smooth engage.
Old 06-02-2019, 05:26 AM
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The link MudRunner posted is pretty detailed when you find the right page. As Carbo said, the switch works when you take the drive out of gear, it's not a factor going into gear. The load on the cluch dogs won't let them release. That instant of grounding the ignition removes enough of the load to let the clutch release easily. I had an old 120 mercruiser that I worked on the adjustment for a couple of weeks trying to get it right. I wish I had the link MudRunner posted back then!

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