3.7 Mercruiser shift interrupt switch

[MTBoat]

I recently put a new shift cable on my 1988 3.7 mercruiser. It now seems to shift into forward or reverse about right.

It does not seem to me that the shift interrupt switch is killing the engine for a split second when it needs to. **My understanding is that should ONLY happen when taking it out of gear in either direction, not putting it into gear??.

1 Question: Exactly how do you adjust the situation so that it interrupts the motor at the exact time....I am not sure what the step by step procedure is, or which cable to adjust to make it do that., top or bottom on the shift assembly?

Any photos or explanations helpful.
Thanks

 

[Bt Doctur]

the interrupter ONLY WORKS in the water , with a load on the propeller coming OUT OF GEAR

 

[achris]

I recently put a new shift cable on my 1988 3.7 mercruiser. It now seems to shift into forward or reverse about right.

It does not seem to me that the shift interrupt switch is killing the engine for a split second when it needs to. **My understanding is that should ONLY happen when taking it out of gear in either direction, not putting it into gear??.

1 Question: Exactly how do you adjust the situation so that it interrupts the motor at the exact time....I am not sure what the step by step procedure is, or which cable to adjust to make it do that., top or bottom on the shift assembly?

Any photos or explanations helpful.
Thanks

Allow me to direct you to 2 posts on the subject. First is an explanation of how the system works, including pictures, and the second is a video of the adjustment procedure.

1. http://forums.iboats.com/mercruiser...nterrupt-system-works-288089.html#post1930449
2. http://youtu.be/-s_tgevX2aI

Cheers,

Chris.....
(and yes, that's me in the video)

 

[Bondo]

It now seems to shift into forward or reverse about right.

Ayuh,...... Sounds good so far,.... Ya gotta go for a boat ride to see if the switch is gonna work,....

Prop load in the water triggers it,.....

 

[MTBoat]

Excellent advice and links, thanks a bunch,,,,will be testing soon in the water.

 

[ematz22]

I have a 3.7 also and my shift interrupt switch activates out of the water on muffs when trying to go in reverse. Will the adjustment procedure fix this or is there an issue with the shift interrupt switch?

 

[sub2010ss]

It's always best to start your own post if you have questions, that way you can describe your problem with your specifications. With that being said, the interior switch must be working if it's killing the engine. It's just a switch so it either works or doesn't. Make the adjustments. They are easy. Then test it out and bring your results back here if something seems off.

 

[Bondo]

I have a 3.7 also and my shift interrupt switch activates out of the water on muffs when trying to go in reverse. Will the adjustment procedure fix this or is there an issue with the shift interrupt switch?

Ayuh,... Welcome Aboard,... It's more likely a need for a new lower shift cable,.....

 

[MTBoat]

I tested it out and now all works well. However, sometimes I find the engine wants to flood when restarting in neutral, and I see that the carb butterfly gets stuck in one place when the shifter is in neutral, but, if I release the shift to just engage the throttle, the butterfly is free to move where it needs to be. I am wondering if it this is normal, should I just make a habit of ALWAYS releasing the shift to throttle only when starting, or do I have some adjustment issue here. Once I flood it, forget it, I tried max throttle or whatever, but no start,,,,have to wait,,,,then maybe hours later or definitely the next day it will fire right up with no effort.

 

[Bt Doctur]

You should have an electric choke element . With a cold motor the choke plate should be closed to within an 1/8 inch of completely closed.
When you start and warm up the motor the choke plate gradually open up until fully open and a spring in the heater element will keep it open.
When the motor is cold again ,the choke plate might stay in the open position until you move the throttle lever to reset it..
Once the motor is hot the choke plate must remain open otherwise you will flood the motor.