Shift interruptor switch

[Chris Craft Todd]

My boat is a 1988 Chris Craft limited with a Alpha One outdrive. The original engine was removed and a 1992 TBI Mercruiser 7.4L was installed. At the lake today it would not come out of gear without shutting off the engine. After some investigation and searching the net i figured out my shift interruptor switch is not functioning properly. Upon inspection of my shift plate, that is transom mounted, i found 2 black wires coming out of th3 switch that are hooked to nothing. I am wondering where do i hook those up. I've learned that the switch needs a ground source but where do i hook it up on this engine? The engine has an original equipment ecu and distributor with a aftermarket accel coil. I've included a few pictures to help identify what i got. Pic 1 drivers side ecu and harness. Pic 2 passenger side ecu and harness. Pic 3 shifter plate with switch. Pic 4 aftermarket coil. Hope you all can help please. Thanks

 

[harringtondav]

Like to help you Todd, but out of my realm. Many pros here to guide you.

 

[Chris Craft Todd]

Thank you. I will wait for others before doing anything.

 

[achris]

Ok, not helping that 7.4 with TBI was never offered with an Alpha drive, so there's no 'standard' setup to follow... If you can supply me with an engine serial number for the 7.4 TBI engine, I can have a look at the diagrams for it and see the best place to connect the switch...

It looks like a TB-IV module in pic1 in the foreground, but I need the serial number to confirm...

Chris........

 

[Chris Craft Todd]

Where is the serial number located?

 

[Chris Craft Todd]

Serial number on engine or numbers off of ecu?

 

[achris]

Engine serial number...
http://forums.iboats.com/forum/engin...15#post6661415

Also, is the interrupt switch normally open, or normally closed? (Check with a multimeter)

Chris.........

 

[Chris Craft Todd]

I dont know if this helps but this is the knock module used- azca 16168749

 

[Chris Craft Todd]

The interrupt switch is normally open

 

[Chris Craft Todd]

Thanks for looking into this chris

 

[achris]

The interrupt switch is normally open

That's not good. You may need to change it...

To have a correctly operating shift interrupt, a normally closed switch is put in the white wire between the distributor and J2 on the ECU.... When the switch is activated (opened) it stops the signal from the distributor to the ECU and no more sparks, until the switch closes.

I'll get you a part number for a normally closed switch and a work-up list to do it... stand-by.

Chris......

 

[achris]

Ok, you need to replace the switch with a 8M0052936, not expensive...

And make the changes to the wiring like this....

Diagram of the wiring as it is now...



Diagram of how it should be when you're done...



Hope this helps

Chris.......

 

[Bt Doctur]

And unless you have a "soft" throttle hand you`ll be needing the Bravo1 drive

 

[Chris Craft Todd]

I truly appreciate all your assistance and taking the time to help me Chris. I've ordered the part and it will be on its way soon. I will post my outcome when i get it installed. So for future reference i have a 1992 Mercruiser 7.4L with a Thunderbolt IV engine management system right?

 

[achris]

Sorry. Not TB-IV. My mistake, from that angle it looked like a TB-IV module.... You have a 1992 7.4EFI, which is rather odd... As Merc didn't release a 7.4 with EFI until about 1995... And the ECU is either a MEFI1 or MEFI2...

Getting that engine serial number would really help nail down a year...

Chris....

 

[Chris Craft Todd]

Chris,

Switch works great! I wired it in just as your diagram showed and it does in fact kill the engine however not momentarily. I have to figure out how to adjust actuator in relation to cable movement in and out of gear. Thanks for all your help.